Triskelion Prime was the inhabited prime planet of its star system.
Lieutenant Commander Steve Tucker, a crewmember aboard the USS Enterprise-D, was born on this non-Federation planet. In 2369, his planet of origin was listed on the chart "USS Enterprise Personnel Database", which was seen on Jean-Luc Picard's PADD. (TNG: "The Chase" okudagram)
This planet was only mentioned in writing.