"I will finish what Enoch started."
Zul is the descendant of his great-great grandfather, Grand Emperor Enoch, and rose to power as Primarch of the Prime Legion during the Post-Dimensional War era. The remaining members of the Grand Empire lost their leader, Enoch, and Tyranus, their homeworld and base of operations.
For a being looking physically elder, he wields the Dark Spark that was passed on to one descendent to another. However, he was quite frail with a mutilated appearance. He had a distinctive, idiosyncratic bone and facial structure.