Iscream

This "bunny" loves a good ritual or two or three or four. You'll find them in their room preparing a Summoning Circle. If they finish it, decipher the scroll that appears inside the furnace room. Once deciphered, use it on Iscream to thwart their plans, instead summoning a different character to their location. You MUST have seen the circle be finished before the scroll appears. Good luck.