There are several ways to animate the dead. In the 19th century, an alchemical method for animation was developed and spread among certain individuals, though its ultimate origin is obscure.
The resulting being, a venom zombie, has the mind of the original person, but lacks the soul or spirit, making it very different from, say, the sorts of zombies created by vodoun. Such zombies are very fast and strong, lacking the “limiter” on the brain that prevents humans from making full use of the abilities of their muscles.
However, the “limiter” exists in humans because muscles and ligaments are shredded from using them at “full power”. Venom zombies are tougher than humans, so they don’t show such strain as quickly, but they also do not heal.
Venom zombies rot over time, and eventually stop moving unless preserved somehow. As their brains rot, they become more feral, and more susceptible to so-called “affection confusion.”
The “affection confusion” is an infliction suffered by all venom zombies. All such zombies hunger for flesh, though they do not digest their food in any biological way. The longer they exist, and the more they rot, the more they confuse all positive emotions with hunger, making it highly likely that they will eventually lose control and devour those they love.
(The reverse does not happen, however. A venom zombie may eat a stranger because he is hungry, but does not think he loves the stranger.)
Venom zombies can only be destroyed by massive trauma to their rotting flesh, particularly their brain. Once the magick can no longer keep the brain working in the most primitive way, the zombie stops moving.
The alchemical potion needed to create such a zombie is always derived from some sort of poison. The Cult of the Maw has a formula that makes uses of hydrangea poison.
When someone is injected with a small amount of the poison, they get sick, but their brain limiter also turns off, giving the subject some of the speed and strength of a zombie. Those bitten or scratched by a venom zombie, or come into contact with its fluids, are similarly infected with the poison, which is where the term “venom zombie” gets its name.
Of course, too much of the poison and the subject dies, instantly transforming into a venom zombie. This can also happen if one dies for some other reason with some of the venom in their system. In addition, the poison can be injected in a corpse and it will rise as a venom zombie, so long as enough of the brain and nervous system remain for the magick to act upon. This is why very fresh corpses are preferred for creation of venom zombies, and it is not always obvious at first one is dealing with a zombie.
If one knows the poison a particular version of the formula is based upon, the antidote for that poison, applied appropriately, can damage or even “kill” such zombies.