USS Enterprise in orbit of Triacus (2268)
Triacus is a planet located in the vicinity of the planet Marcos XII, and the Federation Starbase 4.
The legend of Triacus noted that the planet was the home to a band of marauders who were making constant war thoughout the Epsilon Indi system. After many centuries, these marauders were defeated by the very individuals who they preyed upon. The legend also mentioned that a powerful evil presence remained on Triacus, awaiting for a catalyst to revive it, allowing it to spread it's evil across the galaxy. This power was personified by Gorgan, the last of the planet's inhabitants.
The Starnes Exploration Party encampment on Triacus
In 2268, Triacus was the site of a Starnes Exploration Party lead by Professor Starnes. On stardate 5038.3, one of the archeologists, Professor Wilkins, accidently released Gorgan, during an excavation of cave near their encampment. It was noted that the destruction of whatever civilization that might have been there was destroyed by some natural catastrophe.
Gorgan influences the children of the expedition and causes their parents to commit suicide. A further attempt is made, and initially successful in escaping from Triacus aboard the USS Enterprise to spread its evil on to Marcos. (TOS: "And the Children Shall Lead")