Underworld

"The Underworld is a term collectively used to refer to the afterlife realms belonging to various mythogies and pagan religions. Unlike Hell or any part of "Satan's Kingdom", the underworlds aren't necessary a bad place, just a place for souls to hang out after they passed away. Heck, most underworlds are practically the same as the living world, except that nearly all of the inhtabitants are, well, dead and they are forced to practice a certain religion for eternity. That do make me wonder: Where do the atheists go after they die anyway, since apparently neither God or gods would take them in?"

- Carl Black.

The Underworld is loose term for all non-Abrahamic realms where people are judged and where the sinners are punished by the deities and demons of their own religions and theologies.

Overview
Each of the mythological underworlds are connected multiple gates that lead to these different underworlds stationed across the borderlands of Hell and Earth such as one that leads to Yamaloka (the Hindu equivalent of Hell), Hades (the Greek Underworld), or Yomi (the Japanese Underworld). These gates are fashioned in a way that fit the aesthetic and theme of the mythology they represent such as the gates of Yomi having artistic Shinto decorations around it. The entities that reside within the Underworld are regarded as Chthonic. They are connected to the circles of Hell, though are not considered part of "Satan's Kingdom".

The concept of an underworld is found in almost every civilization and "may be as old as humanity itself". Common features of underworld myths are accounts of living people making journeys to the underworld, often for some heroic purpose. Other myths reinforce traditions that entrance of souls to the underworld requires a proper observation of ceremony, such as the ancient Greek story of the recently dead Patroclus haunting Achilles until his body could be properly buried for this purpose. Persons having social status were dressed and equipped in order to better navigate the underworld.

Description
A number of mythologies incorporate the concept of the soul of the deceased making its own journey to the underworld, with the dead needing to be taken across a defining obstacle such as a lake or a river to reach this destination. Imagery of such journeys can be found in both ancient and modern art. The descent to the underworld has been described as "the single most important myth for Modernist authors".

List of Underworlds

 * Hell - Abrahamic Underworld ruled by Lucifer and Satan
 * Hades - Greek Underworld ruled by Hades
 * Avernus - Roman Underworld ruled by Pluto
 * Bulu - Fijian Underworld ruled by Ratumaibulu
 * Diyu - Chinese Underworld ruled by Yanluowang
 * Duat - Egyptian Underworld ruled by Osiris
 * Helheim - Norse Underworld ruled by Hel
 * Irkalla - Mesopotamian Underworld ruled by Ereshkigal
 * Mawt - Canaanite Underworld ruled by Mot
 * Mictlan - Aztec Underworld ruled by Mictlāntēcutli
 * Naraka - Hindu Underworld by ruled by Yama
 * Nav - Slavic Underworld ruled by Veles
 * Patala - Indian Underworld ruled by Danavas, Daityas, Yakshas and Nagas
 * Tamag - Mongolian/Turkic Underworld ruled by Erlik
 * Tuonela - Finish Underworld ruled by Tuoni
 * Yomi - Shinto Underworld ruled by Izanami
 * Xibalba - Mayan Underworld ruled by Ah Puch
 * Arcapada - Javanese Hindu Underworld co-ruled by Batara Guru and Togog

Image Sources

 * (Max-bedulenko-iron-gloom.jpg) Iron & Gloom by Max Bedulenko