Sky Knights is a spinoff from the main series. Earlier in the series, in an effort to defeat the Queen, Rebels hired gleasons, the most feared and lethal creatures in the galaxy. Eight feet tall and invisible, they mind link with others of their kind, so what one gleason knows, they all know. They were never civilized.
Rebel payment to the gleasons for helping them: a new hunting ground, an emerging world called Tranxte, a world of castles and knights armed with swords and arrows. The people of Tranxte are helpless against these vicious creatures.
Lady Krys, a Knight of the Realm, discovered the grim situation on Tranxte and rescued a near-dead knight, Sir Galborae. She nursed him back to health and delivered him to Empire authorities with the promise that he would one day lead a great army back to Tranxte to save his people.
Sky Knights is his story.