Despite the popular conception, in Amagi Sayuri's world, Hell freezes over... every year, in fact. Actually, the climate is pretty similar to Montreal-- scorching summers and long, snowy winters. Demons live in Hell, and the majority of them are pretty nice. Hell is ruled by Satan, and the four Great Powers under him: Lucifer, Baal, Beelzebub, and Astarte. Lucifer guards the river of Lethe, where souls who have been so hurt during their lives that time alone could not purify them can erase their memories. Baal guards the Castle of Darkness, where Darkness itself is sealed. Beelzebub is in charge of Hades, the afterlife for dark souls (there are pure souls and dark souls...dark souls are gradually purified in Hades, and then ascend to Elysium). Finally, Astarte guards the Monsters' Forest. Heaven and Hell were once at war, and it was Satan who was responsible for bringing an end to that war.