Castle of pure death for higher level characters

[Meepwizard]

I want to know the most devious traps that you can devise for higher level characters that are still technically possible but really aren't. Any evil trap is welcome (level 15ish) just give me your deadliest traps that you can think of in the most detail possible

[Karl Aegis]

How high of a level are we talking? There's a big difference between a trapdoor in the ceiling dropping several tons of snow on a high level character and the same trapdoor dumping several dimensions on a high level character.

[Koo Rehtorb]

At the bottom of the dungeon there is a lever next to a locked vault. Pulling the lever causes the entire dungeon to explode.

[Braininthejar2]

*A 3 by 3 squares pit trap with an antimagic field and a gelatinous cube at the bottom.

*A tunnel with floor from unworked stone. - a set of three one/use spells (because otherwise it's pretty expensive) - rock to mud, followed by mud to rock, (a tunnel doesn't leave much space to leave the area regardless of reflex save, so characters with no flying/freedom of movement will get stuck in the floor) followed by flash flood.

*fodder undead stalling the party in a room that fills with poison gas. Or better, something that can hide in the gas, like a crimson death.

*A permanent reverse gravity effect that makes an unwary character fall up a shaft into a teleportation circle.

*An underwater tunnel with a dispel magic trap half way through.

* Also a trick from an old adventure - to make it harder to disarm the trap, it can be manually operated - there is a skeleton buried inside the wall, tasked with pulling the lever if it hears a password. (it has a narrow tunnel that allows it to hear, but not accessable from the party's side.) Further down the hall there is a magic mouth set to shout the password if the intruders approach at a given distance without identifying themselves.

[Tohron]

This one requires a bit of preparation, but could be pretty nasty.

First have the NPC, create a lifelike golem, and give it a name (say, "Jorge"). Then, whenever they travel, they change their appearance to look like the golem, and refer to themselves as "Jorge". Meanwhile, the golem is kept in a unassuming room somewhere remote, with little or no traps or defenses.

Meanwhile, that room is constantly being scried on by the NPC or their subordinates. If any adventurers use divination to locate "Jorge" and teleport in for the kill, a whole bunch of powerful traps and constructs are teleported into the room after them including a Dimensional Anchor trap (or an Antimagic Field trap). Very nasty against conventional Scry and Die tactics, since the adventurers won't learn about the danger just by using divination on the room.