Total conversion mods fix [Outdated]

Find the mod's config file located somewhere within the appropriate install directory, eg:
C:\Program Files (x86)\Steam\steamapps\common\Amnesia The Dark Descent

If the mod came with a .bat file to launch it then open it with a text editor. It may reference the config file's location. For example White Night's .bat file reads " Launcher.exe wn_config/main_init.cfg". However, if it doesn't then most mods store their config files within their own config folder with a prefix or inside the main config folder with the config itself having the prefix instead and are generally named "main_init.cfg".

By default the config file should look similar to this:
After editing it should look roughly like this:
Add the following lines to it:
DefaultMainSettingsSDL2 = "config/default_main_settings_sdl2.cfg"
DefaultUserKeysSDL2 = "config/default_user_keys_sdl2.cfg"

Finally to fix the "Fatal Error : Could not init steam" error right click Amnesia: The Dark Descent in your Steam library and click properties. Click "Set launch options..." and enter the path to the mod's config file originating from the Amnesia folder. For White Night this would be "wn_config/main_init.cfg" and can be generally found within the .bat file of the mod. After this the mod should work when Amnesia's launched from Steam.