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The "Coda" (Latin translation for "end") were first encountered in 2373 by the USS Voyager while Captain Kathryn Janeway and Commander Chakotay were returning from an away mission. The shuttle was heavily damaged by electrical interference and was forced down on a planet's surface. Commander Chakotay battled to keep the injured Captain alive who was badly injured during the crash.
Unknown to Janeway, an Alien Presence had entered her cerebral cortex and has invaded her brain, causing her to experience many hallucinations which resulted in her death as the presence manipulated her cortex and forced her into an induced coma to create the illusion that she had died.
Janeway reported an out-of-body experience where she could not see or hear nobody except for the "ghost" of her long dead father who had seemingly come to help her "cross over". In actuality, the facsimile was actually the alien presence in her system that fed on her neural energy however in order to do that, he needed her to voluntarily enter his matrix where his species resided.
Janeway resisted the presence and managed to break out of the hallucination for a few seconds, which gave her the strength to resist the creature more that stalked her. She remarked that he was like a "vulture, praying on people near death." She finally managed to subdue the alien and forced him to retreat back into his matrix.
The "Coda" possess no known technology.
The "Coda" exist in a Matrix. The Matrix is an extra-dimensional realm inhabited by a group of non-corporeal lifeforms who feed on individual consciousness. These lifeforms enter the cerebral cortex of persons who are near death, and cause hallucinations of loved ones in an attempt to convince them to enter their Matrix. They often claim it as a kind of afterlife, a "place of wonder" that can assume any desired form.
The cerebral cortex is the part of the brain involved in many higher level tasks such as language, memory, and consciousness. The cerebral cortex includes the parietal lobes, the occipital lobe, the frontal lobe, and the temporal lobes.
In 2373, one of these lifeforms attempted to entice Kathryn Janeway into the Matrix, posing as her deceased father. She saw through its ruse and refused to enter.
- Taylor, J. (1997) Star Trek Voyager "Coda"