The Locrix are described by Val-Yor as "vicious killing machines" whose goals are to achieve total dominion over the galaxy. They are a mechanical race that uses advanced weapons such as lasers to defeat enemies.
Their first appearance was in the episode "Troq", where the galactic hero Val-Yor arrives on Earth to fight off a group of invading Locrix. Val-Yor recruits the Teen Titans and has them all attack the Locrix. He does not allow Starfire to participate, and constantly ignores her, due to a prejudice he has against Tamaraneans, a race which Val-Yor considers weak. However, Starfire ignores orders and still participates in the battle, also venturing with him into the home planet of the Locrix. Together, the two of them set up a Quantum Eradicator on the planet, which subsequently destroys all of the Locrix on the planet.
It is unknown if any survived, as they didn't join the Brotherhood of Evil. However, one of them appears in the episode "Go!" as a prisoner on the Gordanian ship.