Trap

Beware of the trap! When you step on its square, it activates, then it probably harms you, for example by dropping a rock, sending a boulder, shooting a dark, or blinding you!

Arrow trap

These can fire arrows at you, which generally do little damage, and can therefore be a useful source of arrows.

Boulder trap

This is a trap in two parts. The actual trap is a switch, which when activated by stepping on it, sets a nearby boulder rolling towards you. The existence of these traps can sometimes be inferred by an incongruously placed boulder in a room.

Dart trap

Similar to an arrow trap, but with darts, and therefore less useful.

Fire trap

This will set off a column of flame underneath you, causing significant damage and a permanent drop in maximum HP to those without the fire resistance intrinsic. There is also a chance of carried scrolls and spellbooks burning, potions boiling, and armor being burnt.

Fire traps are only randomly generated in Gehennom.

Hole

Holes simply drop you down a number of levels. 2-3 levels is a typical fall distance, but there is no upper limit, bar extreme improbability, on how many levels it is possible to fall through, although you won't fall beyond the Castle.

The same hole is not guaranteed to lead to the same location, or even the same level, even if an object, monster or pet went through it immediately before you.

Magic trap

The effects of magic traps are many and varied...

Falling rock trap

This triggers a falling rock, which hits you on the head, unless you are wearing some kind of hard hat, in which case the damage is lessened. The rock stays on the ground, so it is possible to use them as a rock source, although the trap will be exhausted eventually.

Early pet deaths are usually due to this type of trap.

Pit

Pits in the ground open up when you walk over them. They require a turn to "climb to the edge" and escape. While in the pit, any light source you are carrying will not travel beyond the walls of the pit.

Spiked pit

These are just pits which do more damage. The spikes are sometimes poisoned, which can be fatal for a character without poison resistance.

Teleporter

This teleports you to a random location on the map, unless it is a vault teleporter located in a closet behind ad aerarium, in which case you are teleported to the vault.

Level teleporter

This teleports you to a random location on a random level. You will rarely be teleported further down than you have already explored.

Portal

This uses the ^ symbol, and is therefore a kind of trap. They are used to transport you between dungeon branches, and between the elemental planes. Temporary portals are generated by the Eye of the Aethiopica.