Redjac
Redjac is an intelligent, non-corporeal and non-humanoid entity which requires a humanoid host to enable it to feed. It has been encountered in the Alpha Quadrant, but its actual place of origin is unknown. Whether Redjac is a unique lifeform or a member of a species of similar lifeforms is also unknown.
It is composed of formless electromagnetic impulses. On the single occasion that it displayed its true form, it appeared as swirling masses of multicolored energy, but it is usually invisible.
To maintain its strength and to continue existing, Redjac needs to feed on the emotions of humanoids, specifically the emotion of fear. It accomplishes this by taking a humanoid as a host, and then using the host's body to commit brutal murders, thereby provoking strong quantities of terror for it to feed on. Redjac appears to be capable of inhabiting a humanoid host for as long as it requires, and can even remain after the death of the host by reanimating the body. It is able to use the host to communicate, and appears to also have access to the thoughts of its host, using them to act convincingly as the host between murders. For unknown reasons, Redjac almost always inhabits males, and kills females.
As well as humanoids, Redjac is also able to inhabit sophisticated computer systems. However, doing so appears to require more effort on Redjac's part than using a humanoid as a host. Redjac's origin is unknown, but it is known to have existed for several centuries. The earliest known appearance was in 1888 on Earth. By 2105, it had left Earth, travelling to the colonies on Mars, where it murdered eight women.
Given Redjac's unusual nature, there have been no confirmed encounters with it for many years.
