Abominations

Abominations are a kind of ritually created undead that have almost little to no supernatural components to their creation.  More often, they come from the use of alchemy, engineering and other scientific methods which utilize the innate supernatural forces in the creatures they are building.  In most cases, the bodies are reanimated by stimulating the parts of the body through various mixtures or mechanical elements.
The most notable form of abominations are the Amalgams created by Fleshweavers, who literally stitch together their creations using the parts of several creations.  Little is known publicly about the actual methodology behind how they create them, but their means have proven to be consistently effective.