The crystal thing is in the cave near the red orcs' camp, It located at the cave where you can find the crystal golem (more specific next to it is a door which are surrounded by wall that I've no idea how to reach it)
Do you mean the end door? The one at the end of the dungeon? If so I reached it and it's still a work in progress. It has yet to have stuff so it might not be a good idea. If I'm wrong please tell me though.
