A viviblix is a species of blix that can temporarily reanimate the dead. In Rise of the Evening Star, Errol Fisk describes the curator of a mortuary as a viviblix, and likely has turned some of the dead in his care to zombies.
At the end of Grip of the Shadow Plague, several skeletons from the museum at Lost Mesa suddenly come to life and help overthrow the preserve. Navarog reveals at the end of Secrets of the Dragon Sanctuary that it was the Sphinx's right-hand man Mr. Lich who made this possible since he is a viviblix. Mr. Lich shows up in the fifth installment, Keys to the Demon Prison, though he does not play much of a part other than reanimating the dead and siding with the demons at Zzyzx, deserting the Sphinx.