This is a helper mod to load maps contained in an asset bundle. It looks through the plugins folder and finds bundles that end with ".mapbundle". It will load them, and make a portal for each bundle. The portal caption will be the name of the scene that was bundled, and the mod's icon will float above it if an icon.png is present in the same directory as the mapbundle. The portals will appear on the spawn platform in Sanctum. You can also use the world portal to teleport to custom maps.
To make a map you'll need a decompiled project of Atlyss. You can follow this tutorial to get one https://github.com/LefiloMandering/Atlyss-Modding-Map-Making/wiki/How-to-import-ATLYSS-into-Unity.
Once you have a working project, you can copy an existing map (that is NOT Sanctum) and edit it how you want. Make sure you have a spawn point with the tag "spawnPoint" since the map loader will make a portal pointing to this tag. The caption on the portal will be the name of the scene you bundle.
If you have custom creeps or items on your map, you can pack those scriptables in their own bundle with a ".scriptable" extension. Maploader will load these bundles and automatically add any creeps, items, skills, quests, and conditions it finds to the game's cache so they can work properly.
When the map is ready, you can bundle it with thunderkit or AssetBundleBrowser. Just make sure the extension is ".mapbundle" so the loader will see it.
If you want to upload the map, remember to include the dependency string of this mod in your manifest.