Brainstorming dungeon events

[OneMoreNameless]

So far I've seen vaults, mobs/swarms of certain enemies, and suicide watch I MEAN escort quests. These are all good, but since each only occurs in certain dungeons we could use more of them. Here are some specific ideas.

* Dungeon tremors. After level generation a moderate number of wall/floor tiles are swapped (checking they don't block the stairs entirely), leading to a more chaotic layout than usual. Additionally, several high level Xorns are spawned. Small chance of occurring in underground dungeons.

* Eddies, whirlpools. Eddies spawn in corridors and each turn push actors one tile down them. Knockback resistance applies and there's a small chance of the effect not occuring each turn (so that any player can force their way through if neccessary). Whirlpools do the same thing in open rooms, drawing actors towards it within a radius of 6 or so. High chance of one or two occurring in underwater dungeons.

* Battlefields. Spawn a much larger number of enemies than usual, but also spawn a handful of high level friendly actors. These would be chosen from a list of thematic pairs. (Orcs vs dwarves, liches vs elven mages ...) A few regular monsters would still appear. Upon entering the level, the player is greeted and must choose between:
a) Joining the cause. The friendlies join your party and will reward you with some powerful loot they found once their targets are routed. However, all enemies become aware of your presence and you are prevented from leaving the level until one side perishes.
b) Sticking to your own quest. The enemies remain hostile and friendlies neutral. You can engage or avoid them as you please.
c) Betraying them. BOTH sides become hostile to you. You may escape the level, but this fails the quest. If you outlast both factions you get an exp bonus depending on how many of the kills were yours.
Rare chance of occurring in most dungeons. The dungeon type would influence the most likely matchups.

* Ambushes. Only a third of the regular number of enemies are initially spawned. Once you reach a spot with roughly the same pathing distance to either stairs, the other 2/3rds are spawned on or near the staircases. All are aggravated. An additional handful spawn around you, akin to a summoning trap. Recall is still possible, but reaching the stairs gets you an achievement (excludes cases where you're over-leveled for the dungeon). Small chance of occurring in dungeons with intelligent bosses, such as Dreadfell.

* Hazardous terrain. It would normally act as an indestructible wall or floor tile, but every turn there would be a chance of it triggering. When triggered, the player get a warning (textual and with particles) then three turns later a 'spell' would be cast from the terrain. Examples: cracked wall that spouts a beam of fire-damaging steam, acid leaks that drip onto a single tile, unstable cliff that causes minor rockslides in cone shape. Descriptions and damage type would depend on zone, but function similarly. They'd damage enemies too but wouldn't trigger unless you were nearby to prevent distant deaths. Small chance of occurring in large numbers, in mostly late-game dungeons.