I have both working moon lanterns, one of them keeps screaming obscenities at me all the time, some fairly graphic sexually in detail what the little pixie will do to me when she gets out.
She is absolutely hilarious. It took me a while to figure out who was randomly swearing at me, then I heard her voice and realized it was the pixie in my inventory.
I
chose to release her on my second playthrough, which made act II much less entertaining
. I would've liked to see more of her.