I always thought a sequel to Williams' Sorcerer would have made for a cool theme, something like "Sorcerer II: The Necromancer". No reason it wouldn't have fit in just as well with the lineup of other Bally SS mythological themes. You'd have a wealth of material about the undead to draw on, and I don't believe a theme along the lines of necromancy has been done before, except in a tongue-in-cheek way like Bone Busters or Ghostbusters, or a license like Walking Dead or Dracula.