Robert Deschaines was a medium, psychic and clairvoyant.
He died in 1983 from a stroke in a young age. While his body was unattended on a mortuary slab, his head was cut and stolen. This was discovered by his horrified parents and relatives during his funeral. Many attributed it to the act of cultists.
New Frontiersman, in their usual conspiracy-theorist mentality, made a connection between this event and the disappearance of prominent creative figures around that time (this happened the same week with Max Shea's disappearance), although they attributed them to Cuban interests.
His brain was cloned and augmented and programmed with horrible visions and concepts. It was the essential part of the Alien Monster's attributes as upon its death, the cloned brain served as a psychic resonant device tranmitting its horrible images to survivors.
While in the real world the existence of paranormal powers is controversial, in the Watchmen universe, the psychic powers of Deschaines were apparently genuine as evidenced by the effect of the Alien Monster. Telepathy is the only extranormal power in the novel (other than Doctor Manhattan's).