Yabbat Ummon Tarru was a princess on Earth-1365 and became its lone survivor. When she was four years old, her earth was involved in an incursion event, where two universes are colliding with each other at the focal point of their Earths. A race of beings called Black Priests came from the parallel Earth, intent on destroying her Earth to save their own universe and killing anyone who stood in their way. She fled into the Library of Worlds, a way station of the multiverse. There she was met by three Black Swans (female beings each of a different appearance) who took her in and raised her to be a Black Swan.