Source code time, here's how to mod it.

1: Make your Leven with the given Assets (or Draw your own from the template!)

2: Open the GameData script and copy along the "BaseLeven" struct

3: Go into r_LevenYard and add your McLeven to spawn (may need to expand the room size)

4: Go to the SaveFunctions & LoadFunctions scripts and add the 'LevenMet' save data (This is so your game can remember who's been introduced & not crash your game upon loading)

Happy Modding!