Preternatural is a species within the Gail Carriger books. They are said to not have souls, and are called "soul-stealer" and "curse-breaker" by vampires and werewolves respectively.
Through skin-to-skin contact, preternaturals cancel out the abilities and vulnerabilities of the supernatural, rendering them temporarily human. They can also cancel out a metanatural's borrowed ability -turning the metanatural "human" and restoring the supernatural abilities to the vampire or werewolf they were stolen from.
Preternaturals are very few in number, with only five existing in the entirety of the Great Britain. When having a child with a human partner, preternaturals breed true, and will have preternatural offspring. Since preternaturals are repulsed by the presence of another preternatural, females who are pregnant often miscarry. Males often leave if their partners are pregnant, so as to spare both themselves and the child. Female preternaturals are much less common than males.
In rare cases, a female preternatural may carry the offspring of either a werewolf or a vampire (as their preternatural ability negates the sterility of either species). This results in a metanatural child.