Diabolus puer

Diabolus puer or 'Devil child' is a race of Semi-Humans born with a said: 'Demons Soul.' This 'Demons Soul' gives them Demonic Blood, allowing them to change form, however, it also gives them 'disfigurements', in the case of Howl Pendragon, a Demonic Left Arm.

Diabolus puer is transmitted by blood of a Demon. It is possible to be born naturally a Diabolus Puer, however the method is unknown.