The Bone Hall
I always loved the Magic Card "Throne of Bone". Opportunities for juvenile humor aside, it conjured up images of twisted horrors entombed in deep dungeons for heroes to excavate and destroy.
The Bone Hall and environs are home to a terrifying aberration of wraith, the Marrow Spirit. Marrow Spirits inhabit the bones of their former bodies and ambush travellers seeking to exact revenge for their own lonely, desolate death. Normally the wraiths are tied to their remains, inhabiting the bones themselves, dormant until a victim approaches. In the Bone Hall, however, they become truly fearsome, able to pass through the bones walls at will, and quickly move to any part of the dungeon, ambushing adventurers from behind. They also work with the other denizens of the dungeon, coordinating their attacks in return for the promise that the killing blow will be theirs.