Holdem is a werewolf Beastfallen. He was originally a prince who ran away from his family when he was caught having an affair and ended up living with Sorena. He asked Sorena to make him a Beastfallen to hide his royal lineage so that he could live out his life in peace. He was entrusted with taking care of Sorena's granddaughter (later revealed to be Albus) after Sorena was executed.

(Source: Wikipedia)