A type of real-life world, habitat or environment created by a high-level demiurgeAI, frequently using distributed godtech or clarketech artifacts. Such worlds often include fantastical elements which are derived from ancient Terragen culture, while other fantasy worlds are based on xenosophont myths and legends, or are simply derived from the imagination of the godlet responsible.
In some cases the godlet will modify an existing planet into a fantasy world, often with significant geological reconstruction. In other cases the fantasy scenario is established inside a newly constructed megastructure. The demiurge will fill the newly constructed environment with all sorts of mystic toys, and may isolate it from the rest of the universe, interacting with the inhabitants occasionally through 'magic', mystic phenomena, and miracles. The godlet may communicate with the inhabitants only through visions, avatars or augmented priests.
Or they make a world that is open to the galaxy, so that visitors and tourists can arrive and experience the wonders of the godlet's realm (sometimes to their peril, as some of these worlds contain dangerous artefacts). In some cases godtech devices taken away from a fantasy world will cease to operate, at other times or from other worlds they work perfectly (and command astronomical prices on the galactic markets!), at still other times anyone seeking to plunder such a world - or even steal the tiniest item, is instantly killed by the local nanodefense systems or some form of clarketech defense.