Aryx were large, two-legged birds that were native to Cerea, a planet situated in the Mid Rim. Kidi Aleri, a Cerean rebel, had experience riding these creatures at some point before Operation Yellow Moon which took place in 4 ABY.
During the aforementioned operation, an Alliance endeavor meant to divert Imperial attention, Alliance General Leia Organa inquired whether Aleri and her fellow team members knew how to ride. Aleri responded by explaining what aryx were like to Organa, and expressing her doubt that riding them would adequately prepare her for the mounts Organa intended to hire on Jaresh, a planet within the Corva sector.
The mention of the aryx in new Star Wars canon first occurred in Moving Target: A Princess Leia Adventure, a 2015 novel authored by Jason Fry and Cecil Castellucci. Conversely, within the Star Wars Legends continuity, the aryx made their initial appearance in the first issue of the Star Wars: Republic comic-book series, penned by Jan Strnad, with illustrations by Anthony Winn, and released by Dark Horse Comics on December 16, 1998.