Riss Clyos served as Green Three, a Rebel pilot within the Rebel Alliance's Green Squadron. A significant engagement they participated in was the Battle of Scarif.
The initial appearance of Riss Clyos was via their X-wing starfighter in the film Rogue One: A Star Wars Story. Later, they were officially identified in Star Wars: Rogue One: The Ultimate Visual Guide, which featured a picture of their helmet, though not of Clyos themselves.