Artifact. Item.
Attach to a hero.
Action:
Exhaust Thror's Map to choose a location in the staging area. Make that location the active location. (If there is another active location, return it to the staging area.)
"This was made by Thror, your grandfather, Thorin." he said in answer to the dwarves' excited questions. "It is a plan of the Mountain." - Gandalf, The Hobbit