The earliest history known of Seraph is that he was apprenticed to Fortean, a Sith leader of a powerful dark side organization called Xendor Alliance (or XA). Serpah shared a close relationship with his master, and was probably the closest to Fortean out of all the members in the alliance.
Training and the Dark Jedi Order
It's thought that although Seraph was most likely trained to be a Sith by Fortean, he probably noted flaws within the Sith philosophy and, striving to make it better, changed parts of it to create what would be known as the Dark Jedi Code and philosophy. He created the Dark Jedi Order, calling the followers of this dark side philosophy "''Jen'jidai''". It's most likely that Fortean knew and supported Seraph's efforts, in hopes that the Jen'jidai would be supporters of the XA and it's members.*
Seraph took many apprentices when he started the order, some who were Sith and others who were rogue or gray Jedi. There were seven of the initial members of the DJO that were either killed in action or defected. They are known as The Fallen Seven.
Shortly after the time of his master's death, Seraph simply disappeared. No one knows where he went, or why. He is presumed dead. The XA splintered into different factions and the DJO created a pattern of falling apart only to be rebuilt over and over again throughout the years.