The misty, translucent wings often seen drifting aimlessly above the deserts and the seas are alive. Native to shallow hypersaline lakes and the planet's numerous salt flats, Halaucus is an Ultra Beast with a diet composed entirely of water, detritus, plankton, and stone. The way it processes its food is unknown, but it results in an odd, nearly homogenous squishy body texture with granules and crystals just under the surface. Its texture lets it shrug off most attacks, and it has also demonstrated incredible endurance when under attack by predators. Though large and presumably edible, the flesh of Halaucus is resilient and regenerative. Even if predators like Irozei and Arrakayit can sneak a bite, Halaucus grows back the missing pieces.
Halaucus is difficult to spot in the wild. When flying, it resembles a cirrus cloud, and its whitish body camouflages it well against white sand, stone, and salt. It is most visible when floating on the surface of the ocean, which it does when feeding on plankton. From below, it is invisible due to the glare of the sun, and it has no aerial predators to worry about. Expeditions out to sea have encountered Halaucus drifting in the waves as it filter-feeds. Its reaction to researchers has been peaceful but uninterested. Tissue samples have been taken without issue, though their properties are not yet fully understood.
Little else is known about Halaucus. It is rarely seen, and has only been encountered up close a handful of times. It prefers to flee when it can, and the threat posed by wild Arrakayit makes it difficult to both capture specimens for lab study and observe them in their natural habitat.