The original Star Trek aliens—apart from Spock of course—the Talosians are native to the planet Talos IV and first appeared in the unaired pilot episode “The Cage.” These large-brained humanoids used their unique mental powers to create an illusory world for Captain Christopher Pike and a survivor of an early crash on their planet by an Earth ship.
Some background history of the Talosians was revealed in the three episodes in which they appeared: “The Cage” and “The Menagerie” parts I and II. Originally not unlike humans and many other humanoid species familiar to Star Trek fans, the Talosians reached a high level of technology before nearly destroying themselves in a nuclear war some 100,000 years ago.
Following the war, the surviving Talosians were forced underground and began using their ability to create illusions to shield themselves from the confinement of life below the surface and the destruction above. Over time these powers became more and more sophisticated, and the Talosians became more and more dependent upon them.
As is often the case with a crutch (or a vice) the routine became insufficient to satisfy their needs and they turned to capturing passing space travelers as a way of procuring new material for their illusions. Using the stories from the cultures of different aliens allowed them to experience new worlds themselves.
The Talosians gained a source of new material in 2236 when the SS Columbia crashed on Talos IV. One human woman named Vina survived, though she was left deformed. The Talosians used their powers of illusion to create a familiar world in which she could live the remainder of her life—a good samaritan deed but also one that gave them new experiences.
A fresh infusion of humanity—and hope—arrived 18 years later in 2254 when the Talosians attracted the Enterprise using a fake distress call. They took Captain Pike prisoner in the hope of mating him with Vina; part of their plan to rebuild their civilization. Their efforts failed, leaving Vina behind with an illusory Pike while the real captain departed. Following this experience, Starfleet banned travel to Talos IV issuing “General Order 7.”
The Talosians ultimately assisted Pike in 2267 when they had Spock essentially hijack the Enterprise and bring the now deformed and chair-bound captain to Talos IV where they used their powers to create a more comfortable world for him. This led to the suspension of General Order 7 so that Pike could live with the Talosians.
The Talosians have only really appeared in the TOS episodes “The Cage” and “The Menagerie,” although a Talosian action figure can be seen on the desk of SETI scientist Rain Robinson in the Voyager episode “Future’s End.”
Although the on-screen story of the Talosians ends with Captain Pike’s return to Talos IV in “The Menagerie,” we have been given a conclusion to those events in the Star Trek literary universe in the novel Burning Dreams. In this story Ambassador Spock is summoned to Talos IV 50 years after the events of “The Menagerie” where he finds that the efforts of Captain Pike have led to a restoration of Talosian society.
The Talosians make another appearance in literary Star Trek in the comic series Telepathy War, published by Marvel Comics. In this story the Talosians take part in the Telepathy Wars against the Dominion and Talos IV is invaded by the Jem’Hadar.