[larsdangly]

I think all quasi-magical powers should be modeled as spells in TFT (unless there is some compelling reason to do it otherwise), as this way you can plug the effect you want to achieve into a fully developed and play tested set of mechanics instead of making up a new set of sub-rules that run along side the standard ones.

In this case, I'd say good solutions are Avert to force them away and some sort of dissolve-enchantment effect to kill them. In principle, I don't see why Remove Thrown Spell wouldn't kill a zombie. It removes any thrown spell, and clearly without a thrown spell running zombies are just piles of bones and goop. Alternatively, you could make up a new spell specific to undead but having similar effects (presumably requiring lower IQ or ST cost because of its limited scope of use)

More generally, I think the best way to model priests is as Hero character types with one or more (but usually not much more) spells.