Omega

A mysterious girl who is first witnessed falling through the central shaft of the Vertical World. She was thrown down from her city as human sacrifice in a ceremony for staving off a famine. But her chance encounter with Ruska sets off a chain of events that might just bring into question the very nature of the Vertical World itself. Duty-bound and somewhat of a tomboy, she is inexplicably drawn to Ruska during their journey and the two come to share an unbreakable bond. [Spoiler] Omega's true identity is actually that of an artificial being created by the Omega System from the same universe that Ruska was originally from. Which was an AI created by Gluon to serve humanity on-board an escaped colony spaceship from a ruined earth. After Gluon's untimely death, it assumes control of the administrative systems of the colony spaceship. In doing so, it begins the construction of a structure of "infinite mass" - the "Vertical World" - in order to save humanity from the gravity well of a black hole. Using bodies imbued with a powerful energy source known as "Omeganium". [/Spoiler] [Spoiler] Omega's appearance stems from Gluon's grand-daugther "Risa". A close friend of Ruska who died during the evacuation of the ruined earth. The Omega System is unable to delete her data and instead reinteprets Risa as a being of utmost importance, designing the "Omegas" in her image. [/Spoiler]