The staircase from the Tomb Chamber leads down to a door. The Shaman's map indicates that this leads to 'Da Boneyard.' After an hour or so of rapid descend through unlit galleries, you come to a closed door.
This deep is treated as a new dungeon. All Wounds are reset (they were full anyway). Other items and abilities that are on a per-adventure basis are also reset. However, provisions and similar items have no chance to spoil between deeps. For reference, this applies to the following...
-Throg's Axe of Mighty Striking
-Throg's Chalice of Night (6 uses for this deep)
-Throg's Mark of Chaos
-Dorgath's Runestone of Destruction (not really relevant because it has never been added to a weapon)
-Carrow's Ring of Invisibility
Also, Carrow has 41 arrows remaining and 7 provisions. Dorgath has 8 firebombs, 5 flash powders, and 10 loaves of Stonebread. If you have forgotten what items your Warrior currently has, you can PM me.