A Ghost Knight is one of four classes of knights within the Republic of the Sphere.
"We don't exist in any document or on any organizational charts, but rumors abound about us and all the things we do. The tales would suggest there are just legions of us, but I don't think so-though it could be that I don't really have a clue as to how many of my brethren there truly are. Like Knights-Errant, we get covertly thrust into situations to look for resolutions, and to implement them if we can do so within our mission parameters. So, while people assume Ghost Knights are real, exactly who we are and how we get chosen is kept very secret."
- Ghost War, p. 80
- Ghost War (novel)