The Elf ranger, Grebs, had just leveled and picked up his animal companion on the way to Thistletop so no one but him was really attached to Ghost. The party makes it to Malfeshnekor's prison and send the Summoner's Eidolon to scout where they see him on the ceiling. The party moves in and the Barghest does some major work on them but the party holds their own and brings him down to 10 HP. Upon reading the polymorph ability of Barghest's an evil notion fills my mind. Grebs had left Ghost outside for fear of the giant monster killing his level one pet (with good reason).
Malfeshnekor turns invisible and flees out the door and slams it shut behind him. Ghost failed his reflex save. By the time they make it outside "Ghost" is lying in a pool of blood with a large gash on this throat. They save him and those in the party who speak Sylvain notice "Ghost's" voice is much deeper since his injury.
I added a crypt full of undead right before the treasure room because the party had utterly ANNIHALATED Nualia and I couldn't end the dungeon without a climactic battle at the end. No one noticed "Ghost" taking down the zombies and skeletons with one hit due to the chaos at the time.
They make it to the Crab inside the Helmet and as the gate comes down locking them in, "Ghost" reveals his true nature and transforms in front of the whole party. The look of shock and horror on everyone's face was priceless, none more so than the Ranger, "My wolf!"
The ensuing battle was tough and exciting. It ended with Grebs shooting down Malfeshnekor from the ceiling as he was using Levitate on the unconscious Tiefling Fighter, Evelthor, to bring him to his waiting maw. One of my favorite sessions so far.