It's my first run going that far, but I end up at a dead-end at dark temple 5 (the one with two switch gates and the spider shrine), with no stairs going down. I've seen Random595 go through vault of Yendor, so I don't know if it's a bug or if i'm just dumb.

Hmmm that seems like a bug. Just reduced that zone by 1 level sounds like the boss didn't spawn which means the Yendor Gate would not spawn.

Ahahaha, it seems the god of spidery chaos did indeed save them this time.