While details of it's true nature have yet to by revealed, it was once categorized by Uatu as a “cosmic threat” and later by Jamie Braddock as the “male version of the Phoenix Force”. It still remains partially unknown if this claims are true but, he did seek to place four people from all races in his celestial city located in another realm of existence. When Jamie’s friend were all kicked out of school he and the others went for a race in the desert but were lost and that was when the First Fallen appeared to them unlocking their abilities. Godfrey Calthrop, Ned Horrocks and Amina Synge, Jamie’s girlfriend became known as the Foursaken and wished Jamie to join them. He declined and instead of returning with them to the Singing City, home of the First Fallen he sought to revive his dead sister and modified her by using his powers. Psylocke was now immune to the powers of reality warpers like himself, Proteus, Mad Jim Jaspers and the Shadow King. This would later play a key role in her enrollment into the Exiles. While confused and angry Betsy demanded to know what was going on when Uatu arrived, thereby proving Jamie was not totally mad and wanted to save all existence claiming it was more then cosmic significance that they stop the Foursaken. However Jamie was taken through a portal and the X-Men follow after him only to by captured, except Psylocke who could not by detected. Unable to sacrifice his sister, instead Jamie gave his life to stop the First Fallen, the Foursaken’s master.
As entity the First Fallen doesn’t age and had accumulated vast knowledge thought the ages. It claimed to rival the power of the Phoenix Force but was unable to stop her from reviving the universe. He was also capable of creating an entire city in an unknown plane of reality and awaken others powers.