The Undead Lair Key open Undead Lair dungeon.
The Undead Lair is a mid-level dungeon that is a source of Potions of Wisdom and the Doom Bow. Entrances to the Undead Lair are dropped from Ghost Gods.
Very powerful traps are camouflaged into the stone floor tiles. They can be destroyed but will detonate when a player gets close to them.