diff --git a/Descent3/Game2DLL.cpp b/Descent3/Game2DLL.cpp
index 1dd1718ae..cf080a73e 100644
--- a/Descent3/Game2DLL.cpp
+++ b/Descent3/Game2DLL.cpp
@@ -573,8 +573,7 @@ bool InitGameModule(const char *name, module *mod) {
 
   // Open the hog file
   if (!cf_OpenLibrary(lib_name)) {
-    tmp_dll_name = Base_directory / "netgames" / name;
-    tmp_dll_name.replace_extension(".d3m");
+    tmp_dll_name = cf_LocatePath(lib_name).u8string().c_str();
     Multi_game_dll_name.clear();
     goto loaddll;
   }
diff --git a/Descent3/ambient.cpp b/Descent3/ambient.cpp
index 7819066d3..518ba27dd 100644
--- a/Descent3/ambient.cpp
+++ b/Descent3/ambient.cpp
@@ -293,7 +293,7 @@ void WriteAmbientData() {
   CFILE *ofile;
 
 #ifndef NEWEDITOR
-  ddio_MakePath(filename, Base_directory.u8string().c_str(), "data", "misc", AMBIENT_FILE_NAME, NULL);
+  ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), "data", "misc", AMBIENT_FILE_NAME, NULL);
 #else
   ddio_MakePath(filename, D3HogDir, "data", "misc", AMBIENT_FILE_NAME, NULL);
 #endif
diff --git a/Descent3/demofile.cpp b/Descent3/demofile.cpp
index d5e33d05e..7ba81f4bb 100644
--- a/Descent3/demofile.cpp
+++ b/Descent3/demofile.cpp
@@ -359,7 +359,7 @@ void DemoToggleRecording() {
     if (stricmp(szfile + (strlen(szfile) - 4), ".dem") != 0) {
       strcat(szfile, ".dem");
     }
-    Demo_fname = Base_directory / "demo" / szfile;
+    Demo_fname = cf_GetWritableBaseDirectory() / "demo" / szfile;
     LOG_INFO.printf("Saving demo to file: %s", Demo_fname.u8string().c_str());
     // Try to create the file
     Demo_cfp = cfopen(Demo_fname, "wb");
@@ -1408,7 +1408,7 @@ bool LoadDemoDialog() {
   //	return false;
   // #else
 
-  std::filesystem::path file = Base_directory / "demo";
+  std::filesystem::path file = cf_GetWritableBaseDirectory() / "demo";
 
   if (DoPathFileDialog(false, file, TXT_VIEWDEMO, {"*.dem"}, PFDF_FILEMUSTEXIST)) {
     Demo_fname = file;
diff --git a/Descent3/game.cpp b/Descent3/game.cpp
index be6ecf6a3..9a74c0a3d 100644
--- a/Descent3/game.cpp
+++ b/Descent3/game.cpp
@@ -1279,7 +1279,7 @@ void DoScreenshot() {
   count = 1;
   while (!done) {
     snprintf(str, sizeof(str), "Screenshot%.3d.png", count);
-    ddio_MakePath(filename, Base_directory.u8string().c_str(), str, NULL);
+    ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), str, NULL);
     infile = (CFILE *)cfopen(filename, "rb");
     if (infile == NULL) {
       done = 1;
diff --git a/Descent3/gamesave.cpp b/Descent3/gamesave.cpp
index 314fb5d34..bd44e1ed6 100644
--- a/Descent3/gamesave.cpp
+++ b/Descent3/gamesave.cpp
@@ -348,7 +348,7 @@ void QuickSaveGame() {
     i = Quicksave_game_slot;
 
     snprintf(filename, sizeof(filename), "saveg00%d", i);
-    ddio_MakePath(pathname, Base_directory.u8string().c_str(), "savegame", filename, NULL);
+    ddio_MakePath(pathname, cf_GetWritableBaseDirectory().u8string().c_str(), "savegame", filename, NULL);
 
     fp = fopen(pathname, "rb");
     if (fp) {
@@ -391,7 +391,7 @@ void SaveGameDialog() {
 #endif
 
   // setup paths.
-  ddio_MakePath(savegame_dir, Base_directory.u8string().c_str(), "savegame", NULL);
+  ddio_MakePath(savegame_dir, cf_GetWritableBaseDirectory().u8string().c_str(), "savegame", NULL);
   //	ddio_MakePath(pathname, savegame_dir, "*.sav", NULL); -unused
 
   // create savegame directory if it didn't exist before.
@@ -543,7 +543,7 @@ void __cdecl LoadGameDialogCB(newuiTiledWindow *wnd, void *data)
 
     LOG_DEBUG.printf("savegame slot=%d", id - SAVE_HOTSPOT_ID);
 
-    ddio_MakePath(savegame_dir, Base_directory.u8string().c_str(), "savegame", NULL);
+    ddio_MakePath(savegame_dir, cf_GetWritableBaseDirectory().u8string().c_str(), "savegame", NULL);
     snprintf(filename, sizeof(filename), "saveg00%d", (id - SAVE_HOTSPOT_ID));
     ddio_MakePath(pathname, savegame_dir, filename, NULL);
 
@@ -586,7 +586,7 @@ bool LoadGameDialog() {
   }
 
   // setup paths.
-  ddio_MakePath(savegame_dir, Base_directory.u8string().c_str(), "savegame", NULL);
+  ddio_MakePath(savegame_dir, cf_GetWritableBaseDirectory().u8string().c_str(), "savegame", NULL);
   ddio_MakePath(pathname, savegame_dir, "*.sav", NULL);
 
   // create savegame directory if it didn't exist before.
diff --git a/Descent3/init.cpp b/Descent3/init.cpp
index ca31afcf4..fcec5fce7 100644
--- a/Descent3/init.cpp
+++ b/Descent3/init.cpp
@@ -1390,12 +1390,12 @@ void LoadGameSettings() {
 void InitIOSystems(bool editor) {
   ddio_init_info io_info;
 
-  // Set the base directory
+  // Set the writable base directory
   int dirarg = FindArg("-setdir");
   int exedirarg = FindArg("-useexedir");
-  std::filesystem::path initial_base_directory;
+  std::filesystem::path writable_base_directory;
   if (dirarg) {
-    initial_base_directory = GameArgs[dirarg + 1];
+    writable_base_directory = GameArgs[dirarg + 1];
   } else if (exedirarg) {
     char exec_path[_MAX_PATH];
     memset(exec_path, 0, sizeof(exec_path));
@@ -1404,15 +1404,28 @@ void InitIOSystems(bool editor) {
       Error("Failed to get executable path\n");
     } else {
       std::filesystem::path executablePath(exec_path);
-      initial_base_directory = executablePath.parent_path();
-      LOG_INFO << "Using working directory of " << Base_directory;
+      writable_base_directory = executablePath.parent_path();
+      LOG_INFO << "Using working directory of " << writable_base_directory;
     }
   } else {
-    initial_base_directory = std::filesystem::current_path();
+    writable_base_directory = std::filesystem::current_path();
   }
 
-  cf_SetBaseDirectory(initial_base_directory);
-  ddio_SetWorkingDir(Base_directory.u8string().c_str());
+  ddio_SetWorkingDir(writable_base_directory.u8string().c_str());
+  cf_AddBaseDirectory(writable_base_directory);
+
+  // Set any additional base directories
+  auto additionaldirarg = 0;
+  while (0 != (additionaldirarg = FindArg("-additionaldir", additionaldirarg))) {
+    const auto dir_to_add = GetArg(additionaldirarg + 1);
+    if (dir_to_add == NULL) {
+      LOG_WARNING << "-additionaldir was at the end of the argument list. It should never be at the end of the argument list.";
+      break;
+    } else {
+      cf_AddBaseDirectory(std::filesystem::path(dir_to_add));
+      additionaldirarg += 2;
+    }
+  }
 
   Descent->set_defer_handler(D3DeferHandler);
 
@@ -2015,7 +2028,7 @@ void SetupTempDirectory(void) {
     exit(1);
   }
   // restore working dir
-  ddio_SetWorkingDir(Base_directory.u8string().c_str());
+  ddio_SetWorkingDir(cf_GetWritableBaseDirectory().u8string().c_str());
 }
 
 void DeleteTempFiles() {
diff --git a/Descent3/menu.cpp b/Descent3/menu.cpp
index 7ddd21713..417cd3800 100644
--- a/Descent3/menu.cpp
+++ b/Descent3/menu.cpp
@@ -1061,51 +1061,55 @@ bool ProcessCommandLine() {
 #define TRAINING_MISSION_NAME "Pilot Training"
 
 /**
- * Count singleplayer missions in directory. Mission should have .mn3 extension.
- * @param missions_directory where to search missions. Should be a valid directory.
+ * Count singleplayer missions in directories. Mission should have .mn3 extension.
+ * @param missions_directories where to search missions. Should be a list of valid directories.
  * @return count of found missions
  */
-static inline int count_missions(const std::filesystem::path &missions_directory) {
+static inline int count_missions(const std::vector<std::filesystem::path> &missions_directories) {
   int c = 0;
 
-  ddio_DoForeachFile(missions_directory, std::regex(".*\\.mn3"), [&c](const std::filesystem::path &path) {
-    if (stricmp(path.filename().u8string().c_str(), "d3_2.mn3") == 0)
-      return;
-    LOG_DEBUG.printf("Mission path: %s", path.u8string().c_str());
-    tMissionInfo msninfo{};
-    GetMissionInfo(path.filename().u8string().c_str(), &msninfo);
+  for (const auto &missions_directory : missions_directories) {
+    ddio_DoForeachFile(missions_directory, std::regex(".*\\.mn3"), [&c](const std::filesystem::path &path) {
+      if (stricmp(path.filename().u8string().c_str(), "d3_2.mn3") == 0)
+        return;
+      LOG_DEBUG.printf("Mission path: %s", path.u8string().c_str());
+      tMissionInfo msninfo{};
+      GetMissionInfo(path.filename().u8string().c_str(), &msninfo);
 
-    if (msninfo.name[0] && msninfo.single) {
-      LOG_DEBUG.printf("Name: %s", msninfo.name);
-      c++;
-      if (!(c % 2))
-        DoWaitMessage(true);
-    } else {
-      LOG_DEBUG.printf("Illegal or multiplayer mission: %s", path.u8string().c_str());
-    }
-  });
+      if (msninfo.name[0] && msninfo.single) {
+        LOG_DEBUG.printf("Name: %s", msninfo.name);
+        c++;
+        if (!(c % 2))
+          DoWaitMessage(true);
+      } else {
+        LOG_DEBUG.printf("Illegal or multiplayer mission: %s", path.u8string().c_str());
+      }
+    });
+  }
 
   return c;
 }
 
 static inline int generate_mission_listbox(newuiListBox *lb, int n_maxfiles, char **filelist,
-                                           const std::filesystem::path &missions_directory) {
+                                           const std::vector<std::filesystem::path> &missions_directories) {
   int c = 0;
-  ddio_DoForeachFile(
-      missions_directory, std::regex(".*\\.mn3"), [&c, &lb, &n_maxfiles, &filelist](const std::filesystem::path &path) {
-        tMissionInfo msninfo{};
-        if (c < n_maxfiles) {
-          if (stricmp(path.filename().u8string().c_str(), "d3_2.mn3") == 0)
-            return;
-          if (GetMissionInfo(path.filename().u8string().c_str(), &msninfo) && msninfo.name[0] && msninfo.single) {
-            filelist[c] = mem_strdup(path.filename().u8string().c_str());
-            lb->AddItem(msninfo.name);
-            c++;
-            if (!(c % 2))
-              DoWaitMessage(true);
+  for (const auto &missions_directory : missions_directories) {
+    ddio_DoForeachFile(
+        missions_directory, std::regex(".*\\.mn3"), [&c, &lb, &n_maxfiles, &filelist](const std::filesystem::path &path) {
+          tMissionInfo msninfo{};
+          if (c < n_maxfiles) {
+            if (stricmp(path.filename().u8string().c_str(), "d3_2.mn3") == 0)
+              return;
+            if (GetMissionInfo(path.filename().u8string().c_str(), &msninfo) && msninfo.name[0] && msninfo.single) {
+              filelist[c] = mem_strdup(path.filename().u8string().c_str());
+              lb->AddItem(msninfo.name);
+              c++;
+              if (!(c % 2))
+                DoWaitMessage(true);
+            }
           }
-        }
-      });
+        });
+  }
 
   return c;
 }
@@ -1182,8 +1186,9 @@ bool MenuNewGame() {
   // add mission names to listbox
   // count valid mission files.
   // add a please wait dialog here.
+  auto missions_directories = cf_LocateMultiplePaths("missions");
   n_missions = 0;
-  n_missions += count_missions(D3MissionsDir);
+  n_missions += count_missions(missions_directories);
   if (n_missions) {
     // allocate extra mission slot because of check below which adds a name to the filelist.
     filelist = (char **)mem_malloc(sizeof(char *) * (n_missions + 1));
@@ -1196,7 +1201,7 @@ bool MenuNewGame() {
     goto missions_fail;
   }
   // generate real listbox now.
-  generate_mission_listbox(msn_lb, n_missions, filelist, D3MissionsDir);
+  generate_mission_listbox(msn_lb, n_missions, filelist, missions_directories);
   // #ifdef RELEASE
   int k;
   for (k = 0; k < n_missions; k++) {
diff --git a/Descent3/multi.cpp b/Descent3/multi.cpp
index f1825e6b2..543d298ed 100644
--- a/Descent3/multi.cpp
+++ b/Descent3/multi.cpp
@@ -8010,23 +8010,23 @@ char *GetFileNameFromPlayerAndID(int16_t playernum, int16_t id) {
     break;
   case NETFILE_ID_SHIP_TEX:
     if (NetPlayers[playernum].ship_logo[0])
-      ddio_MakePath(rval, Base_directory.u8string().c_str(), "custom", "graphics", NetPlayers[playernum].ship_logo, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "graphics", NetPlayers[playernum].ship_logo, NULL);
     break;
   case NETFILE_ID_VOICE_TAUNT1:
     if (NetPlayers[playernum].voice_taunt1[0])
-      ddio_MakePath(rval, Base_directory.u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt1, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt1, NULL);
     break;
   case NETFILE_ID_VOICE_TAUNT2:
     if (NetPlayers[playernum].voice_taunt2[0])
-      ddio_MakePath(rval, Base_directory.u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt2, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt2, NULL);
     break;
   case NETFILE_ID_VOICE_TAUNT3:
     if (NetPlayers[playernum].voice_taunt3[0])
-      ddio_MakePath(rval, Base_directory.u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt3, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt3, NULL);
     break;
   case NETFILE_ID_VOICE_TAUNT4:
     if (NetPlayers[playernum].voice_taunt4[0])
-      ddio_MakePath(rval, Base_directory.u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt4, NULL);
+      ddio_MakePath(rval, cf_GetWritableBaseDirectory().u8string().c_str(), "custom", "sounds", NetPlayers[playernum].voice_taunt4, NULL);
     break;
   default:
     LOG_FATAL.printf("Unknown id (%d) passed to GetFileNameFromPlayerAndID()", id);
diff --git a/Descent3/multi_dll_mgr.cpp b/Descent3/multi_dll_mgr.cpp
index fe678480b..d7e3d961d 100644
--- a/Descent3/multi_dll_mgr.cpp
+++ b/Descent3/multi_dll_mgr.cpp
@@ -520,6 +520,9 @@ void GetMultiAPI(multi_api *api) {
   api->fp[109] = (int *)GetRankIndex;
   api->fp[110] = (int *)CheckGetD3M;
   api->fp[111] = (int *)ddio_DoForeachFile;
+  api->fp[112] = (int *)cf_LocatePath;
+  api->fp[113] = (int *)cf_LocateMultiplePaths;
+  api->fp[114] = (int *)cf_GetWritableBaseDirectory;
 
   // Variable pointers
   api->vp[0] = (int *)&Player_num;
@@ -527,7 +530,7 @@ void GetMultiAPI(multi_api *api) {
   api->vp[2] = (int *)&Game_is_master_tracker_game;
   api->vp[3] = (int *)&Game_mode;
   api->vp[4] = (int *)NULL; // Current_pilot; no longer a struct
-  api->vp[5] = (int *)&Base_directory;
+  api->vp[5] = (int *)NULL; // Base_directory; no longer exists
   api->vp[6] = (int *)&MultiDLLGameStarting;
   api->vp[7] = (int *)MTPilotinfo;
   api->vp[8] = (int *)&Num_network_games_known;
@@ -598,7 +601,7 @@ int LoadMultiDLL(const char *name) {
   if (MultiDLLHandle.handle)
     FreeMultiDLL();
 
-  std::filesystem::path dll_path_name = Base_directory / "online";
+  std::filesystem::path dll_path_name = cf_GetWritableBaseDirectory() / "online";
   ddio_DoForeachFile(dll_path_name, std::regex(".+\\.tmp"), [](const std::filesystem::path& path, ...) {
     std::error_code ec;
     std::filesystem::remove(path, ec);
@@ -616,7 +619,7 @@ int LoadMultiDLL(const char *name) {
 
   // Open the hog file
   if (!cf_OpenLibrary(lib_name)) {
-    tmp_dll_name = Base_directory / "online" / name;
+    tmp_dll_name = std::filesystem::path("online") / name;
     tmp_dll_name.replace_extension(".d3c");
     Multi_conn_dll_name.clear();
     goto loaddll;
diff --git a/Descent3/multi_ui.cpp b/Descent3/multi_ui.cpp
index 5a6bf2134..7ff191151 100644
--- a/Descent3/multi_ui.cpp
+++ b/Descent3/multi_ui.cpp
@@ -442,11 +442,12 @@ int MainMultiplayerMenu() {
 
   std::vector<std::string> dllnames;
 
-  ddio_DoForeachFile(Base_directory / "online", std::regex(".*\\.d3c"),
-                     [&dllnames](const std::filesystem::path &path) {
-                       std::string filename = path.stem().string();
+  for (const auto &online_directory : cf_LocateMultiplePaths("online")) {
+    ddio_DoForeachFile(online_directory, std::regex(".*\\.d3c"),
+                       [&dllnames](const std::filesystem::path &path) {
+                         std::string filename = path.stem().string();
 
-                       std::replace(filename.begin(), filename.end(), '~', '/');
+                         std::replace(filename.begin(), filename.end(), '~', '/');
 
                        // Place PXO_NAME first in list
                        if (stricmp(filename.c_str(), PXO_NAME) == 0) {
@@ -455,6 +456,7 @@ int MainMultiplayerMenu() {
                          dllnames.push_back(filename);
                        }
                      });
+  }
 
   for (auto const &name : dllnames) {
     lists->AddItem(name.c_str());
@@ -989,7 +991,7 @@ void DoMultiAllowed(void) {
 }
 
 void MultiDoConfigSave() {
-  std::filesystem::path file = Base_directory / "custom" / "settings";
+  std::filesystem::path file = cf_GetWritableBaseDirectory() / "custom" / "settings";
   if (DoPathFileDialog(true, file, TXT_MULTISAVESET, {"*.mps"}, 0)) {
     file.replace_extension(".mps");
     MultiSaveSettings(file);
@@ -997,7 +999,7 @@ void MultiDoConfigSave() {
 }
 
 void MultiDoConfigLoad() {
-  std::filesystem::path file = Base_directory / "custom" / "settings";
+  std::filesystem::path file = cf_GetWritableBaseDirectory() / "custom" / "settings";
   if (DoPathFileDialog(false, file, TXT_MULTILOADSET, {"*.mps"}, PFDF_FILEMUSTEXIST))
     MultiLoadSettings(file);
 }
diff --git a/Descent3/pilot.cpp b/Descent3/pilot.cpp
index d8db808e4..244aa5871 100644
--- a/Descent3/pilot.cpp
+++ b/Descent3/pilot.cpp
@@ -1581,7 +1581,7 @@ bool PltDelete(pilot *Pilot) {
   std::string pfilename = Pilot->get_filename();
   std::error_code ec;
   if (!pfilename.empty()) {
-    return std::filesystem::remove(Base_directory / pfilename, ec);
+    return std::filesystem::remove(cf_GetWritableBaseDirectory() / pfilename, ec);
   } else {
     Int3(); // this is odd
 
@@ -1595,7 +1595,7 @@ bool PltDelete(pilot *Pilot) {
     PltMakeFNValid(pname);
 
     pfilename = std::string(pname) + PLTEXTENSION;
-    return std::filesystem::remove(Base_directory / pfilename, ec);
+    return std::filesystem::remove(cf_GetWritableBaseDirectory() / pfilename, ec);
   }
 }
 
@@ -1634,7 +1634,7 @@ void PltReadFile(pilot *Pilot, bool keyconfig, bool missiondata) {
     return;
 
   // open and process file
-  std::filesystem::path filename = Base_directory / pfilename;
+  std::filesystem::path filename = cf_GetWritableBaseDirectory() / pfilename;
   try {
     file = cfopen(filename, "rb");
     if (!file)
@@ -1698,7 +1698,7 @@ std::vector<std::string> PltGetPilots(std::string ignore_filename, int display_d
       break;
     }
 
-    ddio_DoForeachFile(Base_directory, wildcard, [&ignore_filename, &result](const std::filesystem::path &path) {
+    ddio_DoForeachFile(cf_GetWritableBaseDirectory(), wildcard, [&ignore_filename, &result](const std::filesystem::path &path) {
       std::string pilot = path.filename().u8string();
       if (!ignore_filename.empty() && stricmp(ignore_filename.c_str(), pilot.c_str()) == 0) {
         LOG_INFO.printf("Getting Pilots... found %s, but ignoring", pilot.c_str());
@@ -3274,7 +3274,7 @@ void _ReadOldPilotFile(pilot *Pilot, bool keyconfig, bool missiondata) {
   std::string pfilename = Pilot->get_filename();
 
   // open and process file
-  std::filesystem::path filename = Base_directory / pfilename;
+  std::filesystem::path filename = cf_GetWritableBaseDirectory() / pfilename;
   CFILE *file = cfopen(filename, "rb");
   if (!file)
     return;
diff --git a/Descent3/pilot_class.cpp b/Descent3/pilot_class.cpp
index c1d91d246..d459fff1a 100644
--- a/Descent3/pilot_class.cpp
+++ b/Descent3/pilot_class.cpp
@@ -415,7 +415,7 @@ int pilot::flush(bool new_file) {
   }
 
   CFILE *file;
-  std::filesystem::path real_filename = Base_directory / filename;
+  std::filesystem::path real_filename = cf_GetWritableBaseDirectory() / filename;
 
   if (new_file && cfexist(real_filename)) {
     // the file already exists, we can't write out
@@ -497,7 +497,7 @@ int pilot::read(bool skip_config, bool skip_mission_data) {
   }
 
   CFILE *file;
-  std::filesystem::path real_filename = Base_directory / filename;
+  std::filesystem::path real_filename = cf_GetWritableBaseDirectory() / filename;
 
   if (!cfexist(real_filename)) {
     // the file already exists, we can't write out
diff --git a/cfile/cfile.cpp b/cfile/cfile.cpp
index ab1a6e095..27475f2fd 100644
--- a/cfile/cfile.cpp
+++ b/cfile/cfile.cpp
@@ -54,8 +54,15 @@ struct library {
   FILE *file = nullptr; // pointer to file for this lib, if no one using it
 };
 
-// The "root" directory of the D3 file tree
-std::filesystem::path Base_directory;
+/* The "root" directories of the D3 file tree
+ *
+ * Directories that come later in the list override directories that come
+ * earlier in the list. For example, if Base_directories[0] / "d3.hog" exists
+ * and Base_directories[1] / "d3.hog" also exists, then the one in
+ * Base_directories[1] will get used. The one in Base_directories[0] will be
+ * ignored.
+ */
+std::vector<std::filesystem::path> Base_directories = {};
 
 // Map of paths. If value of entry is true, path is only for specific extensions
 std::map<std::filesystem::path, bool> paths;
@@ -74,20 +81,32 @@ const char *eof_error = "Unexpected end of file";
 /* This function should be called at least once before you use anything else
  * from this module.
  */
-void cf_SetBaseDirectory(const std::filesystem::path &base_directory) {
-  Base_directory = base_directory;
+void cf_AddBaseDirectory(const std::filesystem::path &base_directory) {
+  if (std::filesystem::exists(base_directory)) {
+    Base_directories.push_back(base_directory);
+  } else {
+    LOG_WARNING << "Ignoring nonexistent base directory: " << base_directory;
+  }
+}
+
+/* After you call this function, you must call cf_AddBaseDirectory() at least
+ * once before you use anything else from this module.
+ */
+void cf_ClearBaseDirectories() {
+  Base_directories.clear();
 }
 
-std::filesystem::path cf_LocatePathCaseInsensitiveHelper(const std::filesystem::path &relative_path) {
+
+std::filesystem::path cf_LocatePathCaseInsensitiveHelper(const std::filesystem::path &relative_path,
+                                                         const std::filesystem::path &starting_dir) {
 #ifdef WIN32
-  std::filesystem::path result = Base_directory / relative_path;
+  std::filesystem::path result = starting_dir / relative_path;
   if (std::filesystem::exists(result)) {
     return result;
   } else {
     return {};
   }
 #else
-  auto &starting_dir = Base_directory;
   // Dumb check, maybe there already all ok?
   if (exists((starting_dir / relative_path))) {
     return starting_dir / relative_path;
@@ -124,20 +143,66 @@ std::filesystem::path cf_LocatePathCaseInsensitiveHelper(const std::filesystem::
 #endif
 }
 
+std::vector<std::filesystem::path> cf_LocatePathMultiplePathsHelper(const std::filesystem::path &relative_path,
+                                                                    bool stop_after_first_result) {
+  ASSERT(("realative_path should be a relative path.", relative_path.is_relative()));
+  std::vector<std::filesystem::path> return_value = { };
+  for (auto base_directories_iterator = Base_directories.rbegin();
+       base_directories_iterator != Base_directories.rend();
+       ++base_directories_iterator) {
+    ASSERT(("base_directory should be an absolute path.", base_directories_iterator->is_absolute()));
+    auto to_append = cf_LocatePathCaseInsensitiveHelper(relative_path, *base_directories_iterator);
+    ASSERT(("to_append should be either empty or an absolute path.", to_append.empty() || to_append.is_absolute()));
+    if (std::filesystem::exists(to_append)) {
+      return_value.insert(return_value.begin(), to_append);
+      if (stop_after_first_result) {
+        break;
+      }
+    }
+  }
+  return return_value;
+}
+
 /**
- * Tries to find a relative path inside of Base_directory.
+ * Tries to find a relative path inside of one of the Base_directories.
  *
  * @param relative_path A relative path that we’ll hopefully find in
- *                      Base_directory. You don’t have to get the capitalization
- *                      of relative_path correct, even on macOS and Linux.
+ *                      one of the Base_directories. You don’t have to get the
+ *                      capitalization of relative_path correct, even on macOS
+ *                      and Linux.
  *
- * @return If the path is found, an absolute path that’s inside
- *         Base_directory. Otherwise, a path that probably doesn’t exist
- *         will be returned.
+ * @return Either an absolute path that’s inside a base directory or an empty
+ *         path if nothing is found.
  */
 std::filesystem::path cf_LocatePath(const std::filesystem::path &relative_path) {
-  ASSERT(("realative_path should be a relative path.", relative_path.is_relative()));
-  return cf_LocatePathCaseInsensitiveHelper(relative_path);
+  auto return_value_list = cf_LocatePathMultiplePathsHelper(relative_path, true);
+  if (return_value_list.empty()) {
+    return "";
+  } else {
+    return return_value_list.front();
+  }
+}
+
+/**
+ * Tries to find multiple relative paths inside of the Base_directories.
+ *
+ * @param relative_path A relative path that we’ll hopefully find in
+ *                      one or more of the Base_directories. You don’t have to
+ *                      get the capitalization of relative_path correct, even on
+ *                      macOS and Linux.
+ *
+ * @return A list of absolute paths. Each path will be inside one of the
+ *         Base_directories.
+ */
+std::vector<std::filesystem::path> cf_LocateMultiplePaths(const std::filesystem::path &relative_path) {
+  return cf_LocatePathMultiplePathsHelper(relative_path, false);
+}
+
+/* Not all Base_directories are necessarily writable, but this function will
+ * return one that should be writable.
+ */
+std::filesystem::path cf_GetWritableBaseDirectory() {
+  return Base_directories.front();
 }
 
 // Generates a cfile error
@@ -154,8 +219,8 @@ static void cf_Close();
 static CFILE *open_file_in_lib(const char *filename);
 
 // Opens a HOG file.  Future calls to cfopen(), etc. will look in this HOG.
-// Parameters:  libname - path to the HOG file, relative to Base_directory.
-// NOTE:	libname must be valid for the entire execution of the program.  Therefore, Base_directory
+// Parameters:  libname - path to the HOG file, relative to one of the Base_directories.
+// NOTE:	libname must be valid for the entire execution of the program.  Therefore, Base_directories
 // 			must not change.
 // Returns: 0 if error, else library handle that can be used to close the library
 int cf_OpenLibrary(const std::filesystem::path &libname) {
diff --git a/cfile/cfile.h b/cfile/cfile.h
index e49ea579b..427964281 100644
--- a/cfile/cfile.h
+++ b/cfile/cfile.h
@@ -140,31 +140,63 @@ enum CFileExitStatus {
   CFES_IN_LIBRARY,
 };
 
-// The "root" directory of the D3 file tree
-extern std::filesystem::path Base_directory;
+/* The "root" directories of the D3 file tree
+ *
+ * Directories that come later in the list override directories that come
+ * earlier in the list. For example, if Base_directories[0] / "d3.hog" exists
+ * and Base_directories[1] / "d3.hog" also exists, then the one in
+ * Base_directories[1] will get used. The one in Base_directories[0] will be
+ * ignored.
+ */
+extern std::vector<std::filesystem::path> Base_directories;
 
 /* This function should be called at least once before you use anything else
  * from this module.
  */
-void cf_SetBaseDirectory(const std::filesystem::path &base_directory);
+void cf_AddBaseDirectory(const std::filesystem::path &base_directory);
+
+/* After you call this function, you must call cf_AddBaseDirectory() at least
+ * once before you use anything else from this module.
+ */
+void cf_ClearBaseDirectories();
 
 /**
- * Tries to find a relative path inside of Base_directory.
+ * Tries to find a relative path inside of one of the Base_directories.
  *
  * @param relative_path A relative path that we’ll hopefully find in
- *                      Base_directory. You don’t have to get the capitalization
- *                      of relative_path correct, even on macOS and Linux.
+ *                      one of the Base_directories. You don’t have to get the
+ *                      capitalization of relative_path correct, even on macOS
+ *                      and Linux.
  *
- * @return An absolute path that’s inside Base_directory.
+ * @return Either an absolute path that’s inside Base_directory or an empty path
+ *         if nothing is found.
  */
 std::filesystem::path cf_LocatePath(const std::filesystem::path &relative_path);
 
+/**
+ * Tries to find multiple relative paths inside of the Base_directories.
+ *
+ * @param relative_path A relative path that we’ll hopefully find in
+ *                      one or more of the Base_directories. You don’t have to
+ *                      get the capitalization of relative_path correct, even on
+ *                      macOS and Linux.
+ *
+ * @return A list of absolute paths. Each path will be inside one of the
+ *         Base_directories.
+ */
+std::vector<std::filesystem::path> cf_LocateMultiplePaths(const std::filesystem::path &relative_path);
+
+/* Not all Base_directories are necessarily writable, but this function will
+ * return one that should be writable.
+ */
+std::filesystem::path cf_GetWritableBaseDirectory();
+
 // See if a file is in a hog
 bool cf_IsFileInHog(const std::filesystem::path &filename, const std::filesystem::path &hogname);
 
 // Opens a HOG file.  Future calls to cfopen(), etc. will look in this HOG.
-// Parameters:  libname - path to the HOG file, relative to Base_directory.
-// NOTE:	libname must be valid for the entire execution of the program.  Therefore, Base_directory
+// Parameters:  libname - path to the HOG file, relative to one of the Base_directories.
+// NOTE:	libname must be valid for the entire execution of the program.  Therefore, Base_directories
 // 			must not change.
 // Returns: 0 if error, else library handle that can be used to close the library
 int cf_OpenLibrary(const std::filesystem::path &libname);
diff --git a/cfile/tests/cfile_tests.cpp b/cfile/tests/cfile_tests.cpp
index 3ca94f0d0..c2b046878 100644
--- a/cfile/tests/cfile_tests.cpp
+++ b/cfile/tests/cfile_tests.cpp
@@ -22,12 +22,12 @@
 #include <gtest/gtest.h>
 #include "cfile.h"
 
-void set_base_directory_to_cwd() {
-  cf_SetBaseDirectory(std::filesystem::current_path());
+void add_cwd_to_base_directories() {
+  cf_AddBaseDirectory(std::filesystem::current_path());
 }
 
 TEST(D3, CFileIO) {
-  set_base_directory_to_cwd();
+  add_cwd_to_base_directories();
   int lib_handle = cf_OpenLibrary("TestDir/test.hog");
   CFILE *file_handle = cfopen("lowercase.txt", "rb");
   char buf[5];
@@ -48,7 +48,7 @@ TEST(D3, CFileIO) {
 }
 
 TEST(D3, CFileLibrary) {
-  set_base_directory_to_cwd();
+  add_cwd_to_base_directories();
   // First pass - without search path in "TestDir" (i.e. not search actual files in directory)
   // Second pass - with search path (files in directory goes first)
   for (int i = 0; i < 2; i++) {
@@ -93,7 +93,8 @@ TEST(D3, CFileLocatePath) {
 
   for (auto const &item : test_paths) {
     auto directory = cwd / item.parent_path();
-    cf_SetBaseDirectory(directory);
+    cf_ClearBaseDirectories();
+    cf_AddBaseDirectory(directory);
     std::filesystem::path file = item.filename();
     std::string file_lc = item.filename().u8string();
     std::transform(file_lc.begin(), file_lc.end(), file_lc.begin(), ::tolower);
diff --git a/ddio/sdlcontroller.cpp b/ddio/sdlcontroller.cpp
index f8101d120..50b70b182 100644
--- a/ddio/sdlcontroller.cpp
+++ b/ddio/sdlcontroller.cpp
@@ -1397,93 +1397,97 @@ int CTLLex(const char *command) {
   return INFFILE_ERROR;
 }
 
-// okay, now search for a '****.ctl' file in the current directory.
+// okay, now search for a '****.ctl' file in the Base_directories
 void sdlgameController::parse_ctl_file(int devnum, const char *ctlname) {
-  // parse each file until we find a name match, no name match, just return
-  ddio_DoForeachFile(
-      Base_directory, std::regex(".*\\.ctl"), [this, &devnum, &ctlname](const std::filesystem::path &path) {
-        InfFile file;
-        bool found_name = false;
-
-        if (file.Open(path.filename(), "[controller settings]", CTLLex)) {
-          // parse each line, setting the appropriate values, etc.
-          while (file.ReadLine()) {
-            int cmd;
-            char operand[128];
-
-            while ((cmd = file.ParseLine(operand, INFFILE_LINELEN)) > INFFILE_ERROR) {
-              // we want to assert that the name command comes before any other to verify
-              // this is the file we really want to change.
-              switch (cmd) {
-              case CTLCMD_NAME:
-                if (strcmp(ctlname, operand) != 0)
-                  goto cancel_file_parse;
-                found_name = true;
-                break;
-
-              case CTLCMD_DEAD: // deadzone
-                if (!found_name)
-                  goto cancel_file_parse;
-                else {
-                  m_ControlList[devnum].deadzone = atof(operand);
-                }
-                break;
-
-              case CTLCMD_AXIS: // allowable axis.
-                                // format of command is "+Z-R"
-                                //	this would add a Z axis to the controller.  -R would remove the Rudder.
-                                // you can do this for X,Y,Z,R,U,V.
-                if (!found_name)
-                  goto cancel_file_parse;
-                else {
-                  int slen = strlen(operand);
-                  for (int i = 0; i <= slen; i += 2) {
-                    int axis_flag;
-                    if ((i + 1) <= slen) {
-                      char axis_cmd = tolower(operand[i + 1]);
-                      if (axis_cmd == 'x')
-                        axis_flag = CTF_X_AXIS;
-                      else if (axis_cmd == 'y')
-                        axis_flag = CTF_Y_AXIS;
-                      else if (axis_cmd == 'z')
-                        axis_flag = CTF_Z_AXIS;
-                      else if (axis_cmd == 'r')
-                        axis_flag = CTF_R_AXIS;
-                      else if (axis_cmd == 'u')
-                        axis_flag = CTF_U_AXIS;
-                      else if (axis_cmd == 'v')
-                        axis_flag = CTF_V_AXIS;
-                      else
-                        axis_flag = 0;
-                      if (operand[i] == '+') {
-                        m_ControlList[devnum].flags |= axis_flag;
-                      } else if (operand[i] == '-') {
-                        m_ControlList[devnum].flags &= (~axis_flag);
+  for (auto base_directories_iterator = Base_directories.rbegin();
+       base_directories_iterator != Base_directories.rend();
+       ++base_directories_iterator) {
+    // parse each file until we find a name match, no name match, just return
+    ddio_DoForeachFile(
+        *base_directories_iterator, std::regex(".*\\.ctl"), [this, &devnum, &ctlname](const std::filesystem::path &path) {
+          InfFile file;
+          bool found_name = false;
+
+          if (file.Open(path.filename(), "[controller settings]", CTLLex)) {
+            // parse each line, setting the appropriate values, etc.
+            while (file.ReadLine()) {
+              int cmd;
+              char operand[128];
+
+              while ((cmd = file.ParseLine(operand, INFFILE_LINELEN)) > INFFILE_ERROR) {
+                // we want to assert that the name command comes before any other to verify
+                // this is the file we really want to change.
+                switch (cmd) {
+                case CTLCMD_NAME:
+                  if (strcmp(ctlname, operand) != 0)
+                    goto cancel_file_parse;
+                  found_name = true;
+                  break;
+
+                case CTLCMD_DEAD: // deadzone
+                  if (!found_name)
+                    goto cancel_file_parse;
+                  else {
+                    m_ControlList[devnum].deadzone = atof(operand);
+                  }
+                  break;
+
+                case CTLCMD_AXIS: // allowable axis.
+                                  // format of command is "+Z-R"
+                                  //	this would add a Z axis to the controller.  -R would remove the Rudder.
+                                  // you can do this for X,Y,Z,R,U,V.
+                  if (!found_name)
+                    goto cancel_file_parse;
+                  else {
+                    int slen = strlen(operand);
+                    for (int i = 0; i <= slen; i += 2) {
+                      int axis_flag;
+                      if ((i + 1) <= slen) {
+                        char axis_cmd = tolower(operand[i + 1]);
+                        if (axis_cmd == 'x')
+                          axis_flag = CTF_X_AXIS;
+                        else if (axis_cmd == 'y')
+                          axis_flag = CTF_Y_AXIS;
+                        else if (axis_cmd == 'z')
+                          axis_flag = CTF_Z_AXIS;
+                        else if (axis_cmd == 'r')
+                          axis_flag = CTF_R_AXIS;
+                        else if (axis_cmd == 'u')
+                          axis_flag = CTF_U_AXIS;
+                        else if (axis_cmd == 'v')
+                          axis_flag = CTF_V_AXIS;
+                        else
+                          axis_flag = 0;
+                        if (operand[i] == '+') {
+                          m_ControlList[devnum].flags |= axis_flag;
+                        } else if (operand[i] == '-') {
+                          m_ControlList[devnum].flags &= (~axis_flag);
+                        } else {
+                          goto cancel_file_parse;
+                        }
                       } else {
-                        goto cancel_file_parse;
+                        break; // this should break out of the axis search but continue with the file
                       }
-                    } else {
-                      break; // this should break out of the axis search but continue with the file
                     }
                   }
+                  break;
+
+                case CTLCMD_SX: // allow modification of global sensitivity modifiers
+                case CTLCMD_SY:
+                case CTLCMD_SZ:
+                case CTLCMD_SR:
+                case CTLCMD_SU:
+                case CTLCMD_SV: {
+                  int idx = (cmd - CTLCMD_SX);
+                  m_ControlList[devnum].sensmod[idx] = atof(operand);
+                  break;
+                }
                 }
-                break;
-
-              case CTLCMD_SX: // allow modification of global sensitivity modifiers
-              case CTLCMD_SY:
-              case CTLCMD_SZ:
-              case CTLCMD_SR:
-              case CTLCMD_SU:
-              case CTLCMD_SV: {
-                int idx = (cmd - CTLCMD_SX);
-                m_ControlList[devnum].sensmod[idx] = atof(operand);
-                break;
-              }
               }
             }
+          cancel_file_parse:
+            file.Close();
           }
-        cancel_file_parse:
-          file.Close();
-        }
-      });
+        });
+  }
 }
diff --git a/editor/MainFrm.cpp b/editor/MainFrm.cpp
index 2334e3da9..009fce25a 100644
--- a/editor/MainFrm.cpp
+++ b/editor/MainFrm.cpp
@@ -1460,7 +1460,7 @@ void InitCScripts() {
   CreateNewMine();
 
   //	Setup include directories for OSIRIS
-  ddio_MakePath(path, Base_directory.u8string().c_str(), "data", "levels", NULL);
+  ddio_MakePath(path, cf_GetWritableBaseDirectory().u8string().c_str(), "data", "levels", NULL);
 }
 
 // Copied from winmain.cpp
diff --git a/editor/editor_lighting.cpp b/editor/editor_lighting.cpp
index 5f90fffd0..5af799ec2 100644
--- a/editor/editor_lighting.cpp
+++ b/editor/editor_lighting.cpp
@@ -870,7 +870,7 @@ void DoRadiosityForRooms() {
 
   if (save_after_bsp) {
     char filename[_MAX_PATH];
-    ddio_MakePath(filename, Base_directory.u8string().c_str(), "BSPSave.D3L", NULL);
+    ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), "BSPSave.D3L", NULL);
 
     // Save the level to
     SaveLevel(filename);
@@ -1140,7 +1140,7 @@ void DoRadiosityForRooms() {
   SqueezeLightmaps(0, -1);
 
   char filename[_MAX_PATH + 1];
-  ddio_MakePath(filename, Base_directory.u8string().c_str(), "LightSave.D3L", NULL);
+  ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), "LightSave.D3L", NULL);
 
   // Save the level to disk
   SaveLevel(filename);
diff --git a/editor/gameeditor.cpp b/editor/gameeditor.cpp
index d36268a33..efbb05cad 100644
--- a/editor/gameeditor.cpp
+++ b/editor/gameeditor.cpp
@@ -611,7 +611,7 @@ void GameToEditor(bool set_viewer_from_player) {
   if (Temp_level_saved) {
     char filename[_MAX_PATH];
 
-    ddio_MakePath(filename, Base_directory.u8string().c_str(), "GameSave.D3L", NULL); // make explicit path
+    ddio_MakePath(filename, cf_GetWritableBaseDirectory().u8string().c_str(), "GameSave.D3L", NULL); // make explicit path
     LoadLevel(filename);
     Temp_level_saved = 0;
   }
@@ -744,7 +744,7 @@ void EditorToGame() {
   //	set game working directory
   bool set_size = false;
   ddio_GetWorkingDir(Editor_dir, sizeof(Editor_dir));
-  ddio_SetWorkingDir(Base_directory.u8string().c_str());
+  ddio_SetWorkingDir(cf_GetWritableBaseDirectory().u8string().c_str());
 
   Osiris_ResetAllTimers();
 
diff --git a/manage/manage.cpp b/manage/manage.cpp
index 1829baddc..b5429d334 100644
--- a/manage/manage.cpp
+++ b/manage/manage.cpp
@@ -673,11 +673,11 @@ int mng_LoadTableFiles(int show_progress) {
 // the user doesn't want network support
 int mng_InitLocalTables() {
   // Set the local table directory from the base directory.
-  auto base_directory_string = Base_directory.u8string();
-  strncpy(LocalD3Dir, base_directory_string.c_str(), sizeof LocalD3Dir);
+  auto writable_base_directory_string = cf_GetWritableBaseDirectory().u8string();
+  strncpy(LocalD3Dir, writable_base_directory_string.c_str(), sizeof LocalD3Dir);
   LocalD3Dir[sizeof LocalD3Dir - 1] = '\0';
-  if (strlen(LocalD3Dir) != strlen(base_directory_string.c_str())) {
-    LOG_WARNING << "Base_directory is too long to fit in LocalD3Dir, so LocalD3Dir was truncated.";
+  if (strlen(LocalD3Dir) != strlen(writable_base_directory_string.c_str())) {
+    LOG_WARNING << "cf_GetWritableBaseDirectory() is too long to fit in LocalD3Dir, so LocalD3Dir was truncated.";
   }
   LOG_INFO << "Local dir: " << LocalD3Dir;
 
diff --git a/netcon/includes/con_dll.h b/netcon/includes/con_dll.h
index 374217981..9cc7cf963 100644
--- a/netcon/includes/con_dll.h
+++ b/netcon/includes/con_dll.h
@@ -701,6 +701,15 @@ typedef void (*ddio_DoForeachFile_fp)(const std::filesystem::path &search_path,
 const std::function<void(std::filesystem::path)> &func);
 ddio_DoForeachFile_fp DLLddio_DoForeachFile;
 
+typedef decltype(&cf_LocatePath) cf_LocatePath_fp;
+cf_LocatePath_fp DLLcf_LocatePath;
+
+typedef decltype(&cf_LocateMultiplePaths) cf_LocateMultiplePaths_fp;
+cf_LocateMultiplePaths_fp DLLcf_LocateMultiplePaths;
+
+typedef decltype(&cf_GetWritableBaseDirectory) cf_GetWritableBaseDirectory_fp;
+cf_GetWritableBaseDirectory_fp DLLcf_GetWritableBaseDirectory;
+
 int DLLUIClass_CurrID = 0xD0;
 
 #define MAX_NET_GAMES 100
@@ -768,7 +777,6 @@ int DLLGame_mode;
 char *DLLTracker_id;
 int *DLLNum_directplay_games;
 netgame_info *DLLNetgame;
-std::filesystem::path *DLLLocalD3Dir;
 int *DLLMultiGameStarting;
 netplayer *DLLMNetPlayers;
 int MTWritingPilot, MTReadingPilot;
@@ -998,13 +1006,15 @@ int StartMultiplayerGameMenu() {
 
   DLLListRemoveAll(script_list);
 #if (!(defined(OEM) || defined(DEMO)))
-  DLLddio_DoForeachFile(*DLLLocalD3Dir / "netgames", std::regex(".+\\.d3m"),
-                        [&dll_ui_items](const std::filesystem::path& path){
-                          dll_ui_items.insert_or_assign(
-                              path.stem().u8string(),
-                              DLLCreateNewUITextItem(path.stem().u8string().c_str(), UICOL_LISTBOX_LO, -1)
-                              );
-  } );
+  for (const auto &netgames_directory : DLLcf_LocateMultiplePaths("netgames")) {
+    DLLddio_DoForeachFile(netgames_directory, std::regex(".+\\.d3m"),
+                          [&dll_ui_items](const std::filesystem::path& path){
+                            dll_ui_items.insert_or_assign(
+                                path.stem().u8string(),
+                                DLLCreateNewUITextItem(path.stem().u8string().c_str(), UICOL_LISTBOX_LO, -1)
+                                );
+    } );
+  }
 #else
   dll_ui_items.insert_or_assign("Anarchy", DLLCreateNewUITextItem("Anarchy", UICOL_LISTBOX_LO, -1));
   dll_ui_items.insert_or_assign("Capture The Flag", DLLCreateNewUITextItem("Capture The Flag", UICOL_LISTBOX_LO, -1));
@@ -1017,10 +1027,13 @@ int StartMultiplayerGameMenu() {
 #if (!(defined(OEM) || defined(DEMO)))
   msn_list *mi;
 
-  const std::vector<std::pair<std::filesystem::path, std::regex>> search_paths = {
-    {*DLLLocalD3Dir / "data" / "levels", std::regex(".+\\.msn")},
-    {*DLLLocalD3Dir / "missions", std::regex(".+\\.mn3")}
-  };
+  std::vector<std::pair<std::filesystem::path, std::regex>> search_paths = { };
+  for (const auto &levels_directory : DLLcf_LocateMultiplePaths(std::filesystem::path("data") / "levels")) {
+    search_paths.push_back({levels_directory, std::regex(".+\\.msn")});
+  }
+  for (const auto &missions_directory : DLLcf_LocateMultiplePaths("missions")) {
+    search_paths.push_back({missions_directory, std::regex(".+\\.mn3")});
+  }
 
   for (auto const &i : search_paths) {
     DLLddio_DoForeachFile(i.first, i.second, [&mi, &list_1](const std::filesystem::path &path) {
@@ -1074,7 +1087,7 @@ int StartMultiplayerGameMenu() {
   DLLNetgame->flags = NF_RANDOMIZE_RESPAWN;
   DLLNewUIWindowLoadBackgroundImage(main_wnd, "multimain.ogf");
   DLLNewUIWindowOpen(main_wnd);
-  if (DLLMultiLoadSettings(*DLLLocalD3Dir / "custom" / "settings" / "default.mps")) {
+  if (DLLMultiLoadSettings(DLLcf_GetWritableBaseDirectory() / "custom" / "settings" / "default.mps")) {
     DLLEditSetText(mission_name_edit, DLLNetgame->name);
 #if (!(defined(OEM) || defined(DEMO)))
     p = DLLGetMissionName(DLLNetgame->mission);
diff --git a/netcon/includes/mdllinit.h b/netcon/includes/mdllinit.h
index b563ff63d..676b250be 100644
--- a/netcon/includes/mdllinit.h
+++ b/netcon/includes/mdllinit.h
@@ -275,6 +275,9 @@ DLLShowNetgameInfo = (ShowNetgameInfo_fp)API.fp[108];
 // API.fp[109]; // Not used
 DLLCheckGetD3M = (CheckGetD3M_fp)API.fp[110];
 DLLddio_DoForeachFile = (ddio_DoForeachFile_fp)API.fp[111];
+DLLcf_LocatePath = (cf_LocatePath_fp)API.fp[112];
+DLLcf_LocateMultiplePaths = (cf_LocateMultiplePaths_fp)API.fp[113];
+DLLcf_GetWritableBaseDirectory = (cf_GetWritableBaseDirectory_fp)API.fp[114];
 
 DLLMPlayers = (player *)API.players;
 DLLNetgame = (netgame_info *)API.netgame;
@@ -286,7 +289,7 @@ DLLTracker_id = (char *)API.vp[1];
 DLLGame_is_master_tracker_game = API.vp[2];
 DLLGame_mode = *API.vp[3];
 // DLLCurrent_pilot = (pilot *)API.vp[4];
-DLLLocalD3Dir = (std::filesystem::path *)API.vp[5];
+// DLLLocalD3Dir = (std::filesystem::path *)API.vp[5];
 DLLMultiGameStarting = (int *)API.vp[6];
 DLLMTPilotinfo = (vmt_descent3_struct *)API.vp[7];
 DLLNum_network_games_known = API.vp[8];
diff --git a/netcon/mtclient/mtclient.cpp b/netcon/mtclient/mtclient.cpp
index dfdcfbf07..bb30d5d7a 100644
--- a/netcon/mtclient/mtclient.cpp
+++ b/netcon/mtclient/mtclient.cpp
@@ -2132,7 +2132,7 @@ void CheckPXOForAnomalies() {
       if (stricmp(DLLMPlayers[i].tracker_id, DLLMPlayers[j].tracker_id) == 0) {
         // Ok, what we have here is multiple users with the same tracker ID.
         // This is bad. It could be user error, but it could be something worse.
-        std::filesystem::path errfilepath = *DLLLocalD3Dir / "pxo.err";
+        std::filesystem::path errfilepath = DLLcf_GetWritableBaseDirectory() / "pxo.err";
         FILE *errfile = fopen(errfilepath.u8string().c_str(), "at");
         if (errfile) {
           fprintf(errfile, "Dup TID: %s & %s / %s\n", DLLMPlayers[j].callsign, DLLMPlayers[i].callsign,