How do the Cracks In The Ice on level 7 work? I'm a bit hesitant to throw away the first character I've gotten this far to find out - is this how you get the drowning achievement? Also, unrelated question: those levers with the "mass pitting mechanism" scrolls nearby? Nothing appears, at least in the room that I can see. Do they appear elsewhere in the dungeon? Or is this a known bug?
To the best of my knowledge, that lever makes two or three 'platoons' of monsters appear in the connected room immediately below the 'mass pitting' room. I'm not sure what happens if there is no such connected room.
The cracks in the ice will occasionally cast Glacial Burst on their squares. I don't know what the chances/percentages are but that's all I've seen. I think it needs to be a bit more exciting. They spawn in the walls if there is no such room. If you have a wall-destroying skill like Digging Ray, Diggle Beak, Bolt of Mass Destruction, etc, you can actually still fight them haha. There was a bug that made the game crash if you attacked monsters in walls but I think that was fixed recently.
I believe the bug that has them spawning in walls has also been fixed. At least if not permanently fixed it's better and happen less often. They now spawn elsewhere usually above the room if they can't below.
Use the dagger skill switcheroo on a flying enemy above a pool of water, and you drown in this case as well. It also gives you a special message on death i.e. 'killed by a poorly chosen switcheroo' as well.