So, as far as I can tell, the ghostface can only be found in Deep Caverns, right at the end of the game. This confuses the hell out of me - you get the quest right at the beginning of the game, you can't complete it literally until the post-game, and the reward is something that couldn't possibly be of any real use to you at that point (well, no reward is particularly useful in the post-game, the only thing left to do is explore for more content)... is the whole quest a developer joke, maybe?
