Although he appears as a normal man, he is not completely human; because his ancestors draw their blood from the same Deities as the Fiends and Vigoor, he is susceptible to the Blood Curse and therefore is able to be turned into a Fiend.
Although he appears as a normal man, he is not completely human; this was discovered during the Dark Dragon Blade incident. Because his ancestors draw their blood from the same Deities as the Fiends and Vigoor, he is susceptible to the Blood Curse and therefore is able to be turned into a Fiend.