It is an imp historian who shows up to 'borrow' your teleporter stones. If you do not bring one with you into the castle, he will either show up the next time you try to use them, or they will stop working until the point you would have gotten them back.
Okay... I've already gone through the castle scenes, quests, and gotten kicked out of the castle and then thrown in the dungeon. I just finally found my way out of the dungeon. I now have to go back in the dungeon to 'clear' it (fully explore and collect all the items within it). However, without my teleportation stones, clearing anything will take a very long time. I have well over 100 strength, but I still have to make frequent trips to the merchants to sell my loot. Thus, my next step must be to get my "borrowed" teleportation stones back. Please tell me how...