Sarcophagi, carved containers to house the dead. The dead are already restless enough, are you really going to add more hate and discontent to the world?
Typically have better loot than barrels, crates, and small chests, and about the same loot as large chests. Heavily guarded by monsters and occasionally spike traps.
Usually a good place to find all types of gems, especially in Irazur Tomb.