Checkmate appears in the DC series Lanterns after its introduction in Peacemaker season 2.
James Gunn said that Lanterns would feature Checkmate, an organization introduced in “Full Nelson,” the season-two finale of Peacemaker. The series also includes Salvation, an interdimensional prison that was introduced in the same episode. These elements connect Lanterns to another DCU television project while keeping its central story focused on the Green Lantern investigation.
Checkmate is separate from the Green Lantern Corps. The Corps is an intergalactic peacekeeping organization whose members use power rings. Guy Gardner, meanwhile, is identified as a member of the Justice Gang. Each group has a different role within the DCU.
Lanterns follows Hal Jordan and John Stewart as they investigate a murder in Rushville, Nebraska. The case begins as a local mystery but leads to darker discoveries and wider DCU implications. Checkmate's presence indicates that the story can involve Earth-based intelligence or strategic forces in addition to cosmic institutions.
The series is designed to stand alone, even though its events help set up the wider DCU storyline. That balance allows viewers unfamiliar with Peacemaker or the comics to follow the main mystery.