Ruby is a demon on The CW Television Network's Supernatural portrayed mainly by actresses Katie Cassidy and Genevieve Cortese. Created by the writers to expand on the characterization of demons within the series, she first appears in the third season, wherein she assists series protagonists Sam and Dean Winchester in fighting her fellow demons. By the fourth season, she has won Sam's trust and begins training him to kill demons with his psychic powers, though Dean remains fearful of ulterior motives. The character is killed at the end of the fourth season. In the fifteenth season, Ruby returns through flashbacks and a visit to the Empty, the angels' and demons' afterlife.

"No Rest for the Wicked" is the sixteenth and final episode of the third season of The CW television series Supernatural, and the show's sixtieth episode overall. Written by series creator Eric Kripke and directed by Kim Manners, the episode was first broadcast on May 15, 2008. The narrative follows the series' protagonists Sam and Dean Winchester —brothers who travel the continental United States hunting supernatural creatures—as they attempt to save the latter's soul from damnation. Having made a year-long demonic pact in the previous season finale, Dean has just one day left to live. The brothers must track down the demonic overlord Lilith, who holds Dean's contract. Lilith, meanwhile, is entertaining herself by possessing a young girl and terrorizing her family, a homage to the Twilight Zone episode "It's a Good Life".