I just had a necromancer lose 50 hp in a single turn in the 2nd Vault of Yendor. I thought I was safe for one more turn, was planning to quaff a healing potion next.

I could learn a lot more from this if I wasn't stuck unable to examine the dungeon after death. All I can take away from this as-is is "You should examine everything that can possibly hit you in the boss room", which I know I'm probably not going to do next time either, because I'm too lazy

 Perhaps 'ghost mode' after you die would be nice, where you can just float around and examine stuff.

I'd like to add a rewind and replay option at some point. Since the game is deterministic its actually quite easy to record the entire run in a really compressed form (just record player inputs). This would make it trivial to add some sort of replay last 10T option.

This is a feature I would love.