The Kell's Scourge is a Fallen syndicate lead by Siviks, Lost to None introduced in the Black Armory downloadable content pack in Destiny 2: Forsaken.
History
Before the events of the Black Armory, Siviks split from his brother to form his own Fallen faction. Siviks and the faction stole technology from the golden age armory, Black Armory, and began to hide out in The Last City.