Matrix

From Memory Alpha, the free Star Trek reference

For the programming code for holograms, see holomatrix.

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.

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. (VOY: "Coda")