Demons or gui, are prevalent in the Chinese mythological world. Gui also refers to the secondary soul that is separated from the higher soul (hun) at death. The superior soul becomes spirit (shen), and if not treated properly in a ritualistic sense, gui can become a ghost or bad demon. Important demons are Chiyou, who fought against the Yellow Emperor, Huangdi (see Chiyou, Huangdi); Gonggong (see Gonggong), who destroyed one of the pillars of the world with his enormous horn, causing turmoil on earth; and the Four Evils, which any new sovereign had to over-come upon assuming rule. Chiyou had gigantic teeth, was part animal and part man, and had extra eyes and arms. Gonggong was a serpent-human combination, whose follower, the monstrous Xiangliu, ate nine mountains with his nine heads and then vomited up the swamps of the world.