The Underworlds: Tartarus, the Grey Wastes, the Abyss and the Nine Hells

The Underworlds exist beneath the surface of the world of Casiphon (though, like other planes, they are cut off and inaccessible during the Elipation, when magic is absent from the world). Their basic physical form was created by the saviour-titans from the body of Hades Zagreus after the Theagony (the battle between the gods).   The Underworlds' purpose is to drain away the dangerous energies left over from the essence of the destroyer titan Typhon, which saturates Casiphon and has corrosive and corruptive properties towards the saviour-titans and lesser gods, as well as their creations. In addition, the souls of deceased mortals are dangerous, eventually giving rise to monstrous beasts or undead, and are sent by funerary rituals to the Underworlds for purification by the Persephone, the Grave Queen and ruling deity of Tartarus. The purified soul energy is then believed to return to the Prime Material Plane or even to the saviour-titans themselves.   There are said to be nine rivers which flow into the Underworlds from nine entrances in the real world (the so-called Hellmouths). These rivers are saturated with power, and drag away the souls of the dead from the mortal world. Mortals who travel to the Underworlds most often do so by navigating one of the Hellmouths, though such journeys are beyond perilous.   The sentient beings in the Underworlds feed on the energy of souls which did not receive the proper funerary rituals, especially those who died by violent or unnatural means. These souls are more difficult for Persephone to capture.   Tartarus: Tartarus is the central plane of the Underworlds and the home of Persephone, who oversees the workings of the underworld planes. Persephone and her subordinate deities (including the Fates, who are said to spin, measure and cut threads representing the lifetimes of mortals) dwell here. Though they are grim deities involved with death, Persephone is venerated as a necessary power who leads to purification and rebirth, ultimately good for mortalkind.   The Grey Wastes: The Grey Wastes are a vast area of twilight, through which the nine rivers snake on their way to Tartarus and the souls of the dead retain a large part of their living memory and form. This area is inhabited in certain places by evil supernatural beings known as the yugoloths, who are selfish and manipulative fiends.   The Abyss: The nine rivers eventually change to various substances, including clotting blood, searing hot mercury and razor-sharp ice. Souls which were not captured in Tartarus fall into the Abyss, a boundless and terrifying realm of horror and torture. The Abyss is inhabited by supernatural beings called demons, whose vicious and arbitrary cruelty arises from a desire to tear down order and replace it with terrible chaos. Only the most enormously powerful beings, the demon lords and princes such as Orcus, Demogorgon and Olurapheran are able to direct the wild and uncontrollable masses of demons to their own ends.   The Nine Hells: At the centre of the Abyss where the nine rivers enter is an enormous spiral, forming dread kingdoms inhabited by supernatural beings called devils. Devils exist in a strict hierarchy, always seeking to subjugate and systematically exploit those weaker than themselves. They are in constant conflict with the chaotic hordes of demons. The most powerful devils, the archdevils including Baalzebul, Mephistopheles, and Asmodeus, constantly plot and scheme to extend their power over the surface of Casiphon.