To get in you need a rope and Glarial's amulet. A rope rack can be built near the raft to supply the rope. It is not necessary to wear the amulet, simply having it with you is enough. Go to the raft on top of Baxtorian Falls, and ride the raft down. Use a rope on the rock on the small island to the south. Use a rope on the tree. Enter the dungeon and run forward, past the shadow spiders, and into the middle room with fire giants. The resource dungeon is found in the back of the room.