[Phantasm]

Instead of an Ally, have you considered looking at it as a Patron? There is one Pyramid article that does this for starships and their captains (Mal Reynolds would have Serenity as a Patron, f'rex), "The Captain's Boat", and I could see it adapted to Der Kestle from Girl Genius and other inanimate but powerful domiciles. (Such domiciles could also be statted up using Spaceships; there's a Pyramid article for that, too, IIRC, but I don't know the article name or issue number offhand.)