Talosians were once a technologically advanced culture but a nuclear holocaust left their planet virtually uninhabitable and killed most of the species. The survivors of the nuclear war congregated in underground dwellings, where they became dependent on their mental ability to create stunningly real illusions, an ability that had been developed by their ancestors. As their mental powers grew, they lost the ability to use the technology left behind by their ancestors. The Talosians found that life using illusion was addictive, almost like a Human developing a physical and psychological dependence on narcotics. They became bored with the content of the illusions which they had. Their dependence upon these illusions for mental stimuli caused the Talosians to begin capturing space travelers to use as the living basis for their illusions.