Sentence: As for digging the rooms out, some times the matter is simply destroyed and recreated with minimal effort by the dungeon, other times its stored some where else like a pocket dimension and used later, you can even just compress the dirt and stone together breaking physics and call it dungeon stone most stories adventurers can not tunnel through the walls of a dungeon.
Combination: a pocket dimension (root: dimension, modifier: pocket)
Property: extra
Property type: emergent