In the Tales of the Green Lantern Corps Annual #3 story "In the Blackest Night", Katma Tui is sent by the Guardians of the Universe to a lightless region of space known as the Obsidian Deeps, in order to recruit a new Green Lantern to protect that region of space. Despite the absolute darkness of the Deeps, Katma's power ring led her unerringly to a completely fearless and honest resident of the Deeps: Rot Lop Fan. However, as Rot Lop Fan's species had evolved in darkness, they had no concept of light and color, and thus Katma Tui was unable to explain how the power ring worked (it projects solid rays of light manifested by the bearer's will power).