Xaphania was the first to discover that the Authority had lied to the other angels regarding his status as the original Creator and so was banished from the Clouded Mountain. This was the start of the first struggle against the Kingdom of Heaven. Xaphania became the leader of the rebel angels who intervened in human evolution to give mankind consciousness some thirty thousand years ago.
After the defeat of forces of The Authority, Xaphania explained to Will Parry and Lyra Silvertongue that all the windows between the worlds must be sealed to prevent Dust from leaking away into the abyss, and that the subtle knife must be destroyed. She also told them that it would be possible to learn how to travel between worlds, like the angels do and like John Parry did, but it would take a lifetime to do.
Xaphania was tall and winged, appearing naked in human form. She was incredibly old.