I'd go with mostly skeletons and zombies, but with about a quarter of the hit die reserved for a serious nasty. If you're lucky, the PCs will for a while think that the encounter is over, and that the big undead was the BBEG. Then the ravens come to pick the bones, and the villagers who were slain stand up again.
So, something with about 12 HD. Either a skeletal Giant, or a Zombified Minotaur or Troll. Something in that range, anyway.
Edit: Oh, and if we didn't suggest much before, its because we were in shock at the awesomeness of the familiar. Or at least that's my excuse.