One of the three races of Beshaki, the Lumen live in the third that is permanently day. They have what is called day magic, abilities that only the Lumen are born with on this world, although they may also be abilities other magic users have on other worlds. Due to the knowledge the walkers have they know exactly what abilities the Lumen have but apart from them no one else quite understands what day magic is, not even the Umbra and the Arctus, the two other magical races on Beshaki.
For centuries the Lumen have kept their side of the river dividing the day section and the twilight section, but things weren't always that way. There was a time when the Lumen attempted to destroy the Umbra, and planned on moving onto the Arctus when that was done, believing that they had the right to rule over the entirety of Beshaki, and that was when the Lumen Knights came into existence. Now they work to keep peace between the Umbra and the Lumen in an attempt to make amends for what the first Knights attempted.