The Douwd were an extragalactic species made of pure energy, self-described as "immortal beings of disguises and false surroundings". They had the ability to create and destroy on an epic scale; they also maintained the ability to attack through psychic means. They could not bring people back to life, only make illusory recreations of them. The Douwd appeared to be powerful and godlike beings nearly omnipotent, but not omniscient.
Only one individual from the Douwd race was encountered, a being who referred to itself as Kevin Uxbridge while in Human form. In 2313, after living within the Milky Way Galaxy for many millennia, he had been traveling on a ship at sea – taking the form of a thirty-three year old, penniless botany student – when he met a twenty-nine year old composer of Tao-classical music named Rishon. Though her parents disapproved of him, she was smitten with Kevin and proposed marriage to him two hours after they met. He put aside his powers and married Rishon; they would be married for fifty-three years, but Kevin never revealed his true identity to her.
In 2361 – with Rishon 77 years old – the couple moved from the aquatic city New Martim Vaz on Earth to the Federation colony on Delta Rana IV to live out their final years together and to "fall in love all over again".
Unfortunately, in 2366, a warship belonging to a vicious species known as the Husnock attacked the planet. As Kevin possessed a pacifist conscience, he refused to destroy the Husnock attackers outright, instead trying to scare them away with false images. Instead of fleeing, they became "angrier and more cruel", laying waste to the planet. Finally, Rishon left Kevin's side and joined the fight against the Husnock – perishing with the other colonists. When Kevin found her body, he lost control of his emotions; in a fury of blind rage, he summoned his powers and destroyed the Husnock completely – all fifty billion of the species. When Kevin regained his senses and realized what he had done, he was horrified. He used his powers to recreate his house and wife, then sentenced himself to exile as the only living being on Rana IV.
It was here that Captain Jean-Luc Picard and the USS Enterprise-D found Kevin and "Rishon", three days after the attack, apparently the sole survivors of the attack on the planet. The ship's counselor, Deanna Troi, began to sense Kevin's true nature through her telepathic powers; Kevin sensed this himself and used his own powers to implant an endlessly-repeating piece of music in Deanna's mind, distracting her and nearly destroying her mind. He also attempted to drive the Enterprise away, first by attacking the ship with a vessel he created, then by obliterating his home with the warship in hopes that the Enterprise would leave. Eventually, Captain Picard used the ship's transporter to transport Kevin and "Rishon" directly to the bridge of the Enterprise and then confronted them with their true natures. Consumed by regret and remorse over what he had done, Kevin removed the music from Deanna's mind and confessed his "sin" to Captain Picard. Picard's response: "We're not qualified to be your judges. We have no law to fit your crime. You're free to return to the planet... and to make Rishon live again." Uxbridge returned to Rana IV and once again recreated Rishon and his house; Picard and the Enterprise left orbit, Picard remarking, "We leave behind a being of extraordinary power... and conscience. I'm not certain if he should be praised or condemned - only that he should be left alone." (TNG: "The Survivors")