From publisher blurb:
Fueled by a creative passion for designing content of the highest quality to fit at every table, the Cosmic Dragon Breviary is a flavor-packed mini-compendium of 5e options, catalyzed by a simple question from one of my closest friends—the brainiac Dragonborn Wizard player in my game: “Hey, wouldn't it be cool if there were Sun and Moon Dragons?”
“So what are these dragons about? ...Is this only for a space campaign?”
The Cosmic Dragons are a line of neutral dragons—a sort of “missing link,” so to speak, between the righteous Metallic Dragons and the fearsome Chromatic Dragons—that strive to perpetuate the natural balance of the multiverse.
They can be found in a wide array of locales and on nearly every plane, making them a perfect fit for any campaign. Nebula Dragons can thrive anywhere that fine particles abound—from dry, dry deserts to misty mountains cold. And the versatile Planetary Dragons may contest territories otherwise claimed by Green, White, or Red Dragons.
Fellow nerds will especially appreciate the way these dragons incorporate real scientific concepts into D&D mechanics: from Moon Dragons taking on blood moon, blue moon, and supermoon adaptations, to speedy Comet Dragons firing meteors at their foes, and dying Sun Dragons collapsing into black holes that tear open a rift between planes.