This article aims to show how the animal world and the divine world interact to form a shared network of associations within Greek culture, which serves to explore and define the practice of possession (manía). For this purpose, I have chosen to focus on the case study of the mares of Potniai, a small town in Boeotia, whose story is told by Pausanias (9, 8, 1-2): gone mad after drinking from a spring of water with extraordinary powers, they shy, overthrow their master, named Glaucus, and dismember him. The detailed analysis of literary sources shows that these animals are evoked (notably in Euripides) to express certain forms of divine possession, particularly those provoked by Dionysos and the Erinyes. Other ancient sources indeed suggest that in Greek culture the horse has deep affinities with the sphere of madness induced by anger.