Excerpted from The World of the Wilderlands of High Adventure:

Gorm [is] a blue-green orb that appears to be about 2/3 the size of Earth’s Moon. Sages with telescopes can readily discern continents and oceans upon Gorm’s surface, and many speculate at the civilizations and monsters that live there. Gorm revolves around Gaia every 20 days, and rotates on its axis every 30 hours. No major gods claim to represent Gorm; sages believe this is because the gods of the peoples of the moon would never agree to a god of Gaia representing them. The fact that no gods of Gorm have ever made themselves known has little bearing on this theory. Some sages believe that Demon-Gods such as Demogorgon, Dyzan, K’tau, Mynarthitep, Orcus, Tsathoggus, Xiim-Chaasath, Xirchiriog, Yan-Thar, and Yog either are from or at least reside on Gorm.

Summoners find the phases and houses of Gorm to be central in many of their spells and rituals, especially those of the Demon-Gods. Oddly, the moon is holy to many tribes of Cavemen, who hold it to be the Land of the Spirits or the Great Hunting Wood. Fey, too, hold the Blue Moon in some esteem, holding festivals when it is full and hiding in fear when it is new.