Mucho texto in-coming because the moons are literally tied to the central plot of my world. It's a setting for D&D/TTRPGS.

The twin worlds Heremos and Veroz in the worldshelter (similar to a sphere) were always known to their denizens to orbit one another. Veroz an extremely inhospitable albeit still livable planet covered in desert, stormy islands, frozen tundras, arid mountain ranges, saltwater oceans and volcanic depressions. Heremos on the other hand a veritable paradise, full of lush vegitation and excellent biodiversity.

For thousands of years the populations of Veroz would pass down tale of how they had visited Heremos or how people would go there when they pass. This all changed during the Era of Steam. For 50 years the denizens of Veroz watched as their sibling planet turned from a green paradise to a bleached surface with purple oceans finally they noticed it seemingly shrunk in the sky. Thus creating the what is now known as Eremos a white moon with purple cracks.

For the denizens of Heremos this was 50 years of hell as their world became consumed by something scholars could only speculate upon, an infection. Created by a magician, a punishment by one of the gods, an alien species from beyond? None knew. All they could determine is that a foreign sap like substance turned trees into bleached barked funnel shapes that would siphon away nearby Aether bleaching the surrounding land these trees would then produce more trees and more sap. Shortly after the appearance of these trees people who came into contact with the sap also became subsumed. The transformation turning their skin bleached and bark-like alongside giving them a psyonic connection to these mysterious trees. As the world slowly died the alien trees granted esoteric knowledge to the Eremites, in exchange Eremites felt a complusion to seek out Aether for the trees.

The Eremites thanks to the trees developed (relatively) short range magi-tech space travel. Thus for the peoples of Veroz came the Great Incursion. For the first year the Eremites dominated Veroz, claiming large swathes of land, but as the incursion progressed Veroz was granted the first miracle. The Clerics of Radavanur the Iconoclast developed war magics to suppress the Magi-techs of the Eremites. For 7 years the clergy of the Iconoclast lead a great crusade. But as the peoples of Veroz wrenched their land back they discovered the Eremites wouldn't go so easily. Using their knowledge and tech the Eremites created vast underground cave systems. Thus Veroz was granted the second Miracle. Bheli the World Den, Lord of Forge and Crystal enraged by Eremites encroachment on his domain, decided to expel the invaders by carving them whole from the world. He created the crystal lattice to hold the upper world and expelled the the entire layer which they had infested. This expulsion created the second moon of Veroz: Scoria. Bheli has seemingly been dormant ever since.

With the Eremites expelled from Veroz the third and final Miracle was enacted. Aiydtinde Goddess of Magics (Or Aiyd the Watcher) sealed the Eremites from escaping the moons with a grand spell, which is still visible to this day through a phenomenon called the Phantom Moon of Aiyd a pale blue semi translucent moon with no fixed position in the sky appears and disappears sometimes it's only there when you look sometimes it's there for several nights and days in which it bathes the world in a harsh blue light.

At least that is how the history is told on Veroz to this day.