Abhumans are descendants of humans who have physically evolved after being isolated on worlds with various environmental conditions.
In an Imperium where genetic mutation and spiritual corruption are often interrelated, abhumans are a focus of much controversy. In more liberal times under the Emperor, even markedly divergent abhumans such as the Beastmen could serve in the Imperial Guard. Since the Emperor's stasis however, only the lesser deviants, such as Ogryns and Ratlings, are allowed citizenship. However, they are still distrusted by the Puritan members of the Inquisition.