The Sakethan culture was an entity which once had a presence on Calder II.
On that planet, it left behind ancient ruins including burial mounds associated with Romulan artifacts. They also created glyph stones.
By 2370, a Federation science station on the planet was tasked with protecting the Sakethan treasures from looters. (TNG: "Gambit, Part I")
This culture was only mentioned in dialogue.
The Sakethan culture appears to have been related to the Debrune