I've tested this with sigil 1.21 both regular and compat versions.
After killing the barons, and getting the invulnerability sphere, i seem to get stuck in the next room, and I think it's a bug.
You're supposed to hit the switch and descend in the elevator. On your left would be multiple "giant" steps with imps, these are supposed to lower to your level, but they don't. On your right there should be a door with a chainsaw, but it doesn't open.
Can anyone test this? or am I missing something?