[Dead Bad Things]

Invocation seems like all it takes.....invitation maybe not so much..

Zombies have one simple directive and motivation.......Demons are hell bent..so to say..on destruction for various vices, sins, and other malicious endeavors.
They also require certain metaphysical elements to achieve manifestation.

On the other hand....conditions for a zombie outbreak are practically ideal.....whether transmission is spread one bite at a time, or thru mass outbreak.

This are just a few of the ingredients insuring victory for the undead!