Leeya, an empress, forged an alliance between her realm, known as the Regency Worlds, and the Galactic Empire. As a result of this alliance, the Empire allowed the Regency Worlds a certain level of independence and imposed reasonable taxes.
The initial reference to Empress Leeya occurred in Dawn of Rebellion. This canon roleplaying sourcebook, published in 2018, draws its inspiration from Star Wars Rebels and Rogue One: A Star Wars Story. Fantasy Flight Games released the book, and it was written by John Dunn, Tom Sorenson, Sterling Hershey, Jonathan Julius, Keith Ryan Kappel, Tim Huckelberry, Jason Marker, and James M. Spahn.