The Keeper was magistrate of the dying Talosian race of Talos IV. A necklace with a round pendant distinguished him from other Talosians.
The Keeper was charged with the upkeep of the Talosian menagerie, an elaborate test with the aim to find a servant species that was supposed to repopulate the planet later. Under his command, the Talosians rescued Vina, the only survivor of the crashed Earth vessel SS Columbia, and later lured the USS Enterprise to the planet in 2254. The Keeper then sent two Talosian underlings to kidnap Captain Christopher Pike, then captain of the Enterprise, from the surface of the planet.
Using telepathic illusions and a supply of a blue liquid that he claimed was a "nourishing protein complex", The Keeper intended to trap Pike into accepting a life on Talos IV as Vina's mate and breeding stock for a new, stronger race. The Keeper also detailed alternative mating selections from the Enterprise, Number One and Yeoman J.M. Colt, once they were also captured.
Upon being caught and strangled by Pike, The Keeper became threatening, momentarily assuming the appearance of an illusory anthropoid ape. After the captain managed to free himself and the female officers by overcoming The Keepers' mental powers, however, the magistrate had to accept that Humanity was unsuitable for his plans, due to their strong will and refusal to submit to captivity. While Pike and the Enterprise were let go, the magistrate agreed to take care of Vina, even providing her with an illusory Pike to keep her company. Before the real Captain Pike was beamed back aboard the Enterprise, The Keeper wished him, "May you find your way as pleasant."
When Spock attempted to return Pike to Talos IV against orders in 2267, The Keeper remotely took control of a screen in the Enterprise's briefing room, transmitting images of Pike's earlier encounter with the Talosians to a disciplinary hearing aboard the ship. The Keeper later telepathically contacted the ship directly, relaying footage of himself to the screen, and revealed to Captain Kirk – the current captain of the Enterprise – that a witness of the hearing, Commodore José I. Mendez, had actually been yet another illusion, nullifying the hearing. Finally, The Keeper welcomed Pike back to the planet, ensuring it was what the former captain wanted to do, and wished Kirk, "May you find your way as pleasant [as Pike's]."