Douwd

The Douwd are an immortal species which can assume any physical appearance. They have the power to create elaborated illusions and to annihilate entire civilizations with their minds. Fortunately, however, the only known member of this species has a very strong code against killing - although in a moment of unexpected grief and anger he destroyed the Husnock to avenge the death of his Human wife.

Appearances

 * Star Trek: The Next Generation, s03e03, "The Survivors" (1989)