Last Gate of the Emperor

Yared Heywat lives in Addis Prime with his uncle Moti and their bionic lioness, Besa. His skill at an underground augmented-reality game offers an escape from the city's restrictions until logging in under his real name triggers an attack and Moti disappears. Stories his uncle told him about celestial kingdoms and destructive monsters begin to resemble history rather than myth. With Besa and a former gaming rival called the Ibis, Yared searches for Moti and discovers his connection to a conflict extending across the galaxy.