As a member of the party I think that it would be best to get a more defined background for Zeratul. So here is his origin story of sorts
Zeratul was born as a slum rat but at a very early age was adopted by an elven noble household with a catch. If a draft ever came and they needed to send a child. They would send Zeratul. As a result Zeratul was a neglected child trained to fight from birth. He trained with a harsh elven master who had fought in a few wars and definitely had seen more than some bloodshed in his life. Zeratul as a result did not spend any time studying in a library or talking to people. (hence Int/Cha: 8) He spent a lot of his training resisting poison and tracking. His physical attributes were punished to make him stronger. When the draft did come Zeratul left without a word. He was joined with an anti demon strike team full of Ordo Orum and other holy types. His strike team was ordered to attack a small defense tower held by evil forces. The strike team expected a lvl 2ish encounters but the boss demon was there. The boss demon possesses Zeratul because his MD is garbage and uses his body as a vessel to wipe the entire group. However, Zeratul managed to keep the demon contained in his body after it murdered his whole group. When that happened the Demon was permanently fused with Zeratul. The demon specifically was Balanar also known as the Night Stalker. He dramatically increased Zeratul’s abilities. Zeratul also know had a demon in his head at all times to bounce ideas off of. Now if Zeratul dies so does Balanar. Zeratul and Balanar wish to ascend to a greater form together and make the most out of their newly found partnership. Zeratul decided to go to Drakkenhall seeing as the Ordo Orum has the least influence there. He began to work as a vigilante and to make the most out of his powers. He was also very ferocious and earned the attention of a vigilante group known as the Black Roses. He joined up with them which made one of his NPC contacts (Leader of the Black roses stealth type with knowledge of Drakken Hall underworld) He also made contact with Mal Keshar (my old guy) as an expert in dark magic. Mal Keshar helps him develop the demonic sides of his powers. His final NPC contact is his old Instructor who arrived in Drakken Hall after leaving Zeratul’s old family. His master now runs a small martial arts school on the docks. The school also works as a port security contract for merchants.