The Sakethan civilization was an entity which once had a presence on Calder II.
Caldar II was particularly known for its ancient Sakethan ruins, including burial mounds which were associated with Romulan artifacts. The planet also contained Sakethan glyph stones.
By 2370, a Federation science station on the planet was tasked with protecting the Sakethan treasures from looters. (TNG: "Gambit, Part I")
It remains unclear if the Sakethans were themselves Debrune, or merely associated with them.