To enter this dungeon you must hand Jester's Marbles to the Jester that spawns when you use the Summoning Stone at 65.8S 43.8W in Graveyard to be flagged to enter. The marbles are found at 65.1S 43.7W. (Get up on the cliff at 63.5S 44.5W.) While the Jester summons a portal to the dungeon when given the marbles, there is also a fixed location portal in the bunker at 64.8S 44.3W. The flag is permanent and when reentering the dungeon just use the bunker portal.