Devidians in their true form
Devidians were a vaguely humanoid, shapeshifting species native to Devidia II. Their physical characteristics composed of being between 2 and 3 meters in height; they had no apparent eyes but they possessed an orifice on what most humanoids would call their forehead, that resembled a mouth. They lived out of phase with most other lifeforms with a phase variance of 0.004. They also possessed the ability to travel through time.
Devidians' only useful form of nourishment was Human neural energy. They acquired this energy by draining the subject of their neural energy, killing the subject. They preyed on humans from 19th century San Francisco using the cholera epidemic at the time as a cover for their murders.
The Devidians were destroyed in 2369 when the USS Enterprise-D fired modified photon torpedoes on the Devidians' habitat to prevent them from further incursions. (TNG: "Time's Arrow, Part I & Part II")