This one is for ConceptArt.org's Creature of the Week contest, the "Gorgeous Sky Guardian". Here's the text that accompanied my entry:
"A solitary Prismat floats high in the atmosphere above Eradi Par. Entirely dependent on converted solar energy to maintain the high temperatures in its float dome, Prismats must always remain on the sunlit side of the planet, endlessly traveling across the sky. The sun's rays are focused and refracted inside the dome, surrounding the creature in a halo of pure color. Survey teams have noted that many of the planet's other aerial life forms seem to congregate around a nearby Prismat as it passes by, and often predators and prey will be seen cavorting peacefully through the surrounding rainbows."