If you want to test an overlord room design:
1) Get a gamestate where you're standing near the door leading to a living overlord's room, but no one has ever been inside the room (can be done if someone's been in there, see further down).
2) Save.
3) Quit the game.
4) Create a backup copy of the save in a nice safe place
5) Create a backup copy of your \RuntimeData\Logic\RoomMaps\OverlordBossRoom\ folder, in a nice safe place.
6) Empty out \RuntimeData\Logic\RoomMaps\OverlordBossRoom\ .
7) Add the overlord room design you want to test to \RuntimeData\Logic\RoomMaps\OverlordBossRoom\ .
Load the save, enter the overlord room, see what happens.
9) Once done with the test, exit the overlord room, save, quit.
And if the test didn't go perfectly (what, that happens?) :
10) Either:
- copy the backup save over the save's folder; this only works if no one had been in the overlord's room before you made that backup.
- or find the overlord room chunk's .datc file in the region folder of your save and delete it (this will force it to be regenerated from scratch when entered again)
-- * this is also how to start this process from a gamestate where someone's already been in the overlord room.
-- Iirc, the chunk ID of your current room is displayed as a #123 (where 123 is whatever the chunk ID is) on the escape menu.
11) Load the save, enter the overlord room, see what happens.
Have fun
