Talking to the skull-in-a-pentagram still, after a few more questions and requests for payment we couldn't make the Cleric comes up with what she thinks is a spiffy idea. She suggests throwing a sack over the skull, taking it out of the pentagram and carrying it around with us, letting it out whenever we need it.
The sheer brilliance of this idea is only dwarfed by the fact that the Cleric is being played by a friend who used to play with us but can no longer get to sessions, making it to this one through special circumstances. No matter how badly wrong his plan went he wouldn't have to put up with any of the consequences. Genius!