Dragon Knights

The Dragon Knights are an ancient group of the most skilled warriors in Midgard.

Background
Symbolized by the Chinese character 飛 (which actually means "flight" not "rain" as stated in the manhwa), the Dragon Knights existed several hundred years ago during the former part of the Age of Gods. They were known to use advanced sword techniques that were developed and perfected from years of practice. No one knows what happened to them after they vanished, although one reportedly trained Chaos after he was discovered.

(NOTE: It is possible that Rune Knights are either a derivative of Dragon Knights or its modern descendants as Rune Knights in Ragnarok Online can use dragons as mounts. Although the word dragon in the name could refer to the Dragon Knights' level of skill and not have any direct relations to dragons themselves.)