The Douwd made their one and only Star Trek TNG appearance in episode 3x03: "The Survivors". They were a species of extraordinary powers, but with a pacifistic nature. As Captain Picard once said about one of them:
We leave behind a being of extraordinary power... and conscience.
I'm curious if there is ever another mention of the species in any of the other Star Trek series or books.
The Douwd have been mentioned (in passing) in four officially licensed Star Trek books but have never appeared as a character, other than in the original TNG episode, Survivors.
Even the Q recognize a common consensual reality, a certain metaphysical bedrock or foundation that transcends even our own infinite command over time and space, energy and matter. The alternative is utter chaos, and we all understand chat. So do the Organians and the Metrons and the Douwd and all of the other truly advanced intelligences. But not 0, not anymore. He's different now.
Machines were born, sometimes surpassing their makers, and fragile life-forms dared the void between worlds in vessels of every description, leaving their tracks on a thousand systems before shedding their physical forms entirely to become numinous beings of pure thought. There were the Organians, Picard realized, and the Metrons and the Thasians and the Zalkonians and the Douwd.
She had heard tales of a secretive people called the Douwd, beings to whom imaginative thought defined reality, so that they lived lives of illusion and pretense, rarely revealing themselves for what they were-although the one thing they would never do was use their deceptions to harm others.
Their frequent visitor from the Q Continuum had demonstrated his amazing powers for them time and again. Once, he had even granted the first officer a taste of them. “Or the Traveler,” he continued, “who can manipulate the very fabric of space and time. And don’t forget the Douwd, who was able to wipe out an entire race with a single thought.”
Memory Alpha's entry on the Douwd indicates that the episode you reference 'The Survivors' is their only appearance so far. I've seen them pop up once or twice in Fanfic, but never in any of the official books.
