The Underworld is roughly the same size as the Human world, but with a much larger landmass, as there are no oceans just lakes. The sky was originally purple during both the day and night, but the current Four Great Satans adjusted the flow of time to match it in the human world for the sake of the reincarnated Devils. They reproduced an artificial moon using Demonic Powers and made the night's darkness the same with the human world.
The Underworld was originally split into two regions: The Devils' Region and the Fallen Angels' Region, which ended in Volume 4 after the creation of the peace treaty between the leaders of the Three Factions.
The current Capital of the Satan territory previously ruled by Sirzechs Lucifer and now being ruled by Ajuka Beelzebub. It has one of the most advanced hospitals, which is named Serafall Memorial Hospital. During the Demonic Beast Riot, the city came under attack by the Bandersnatch and Jabberwocky created by Annihilation Maker, forcing an evacuation of the city residents.
Serafall Memorial Hospital
A hospital created by the former heiress Serafall Leviathan from the natural reserves of her clan. It is famously known throughout the Underworld to not only the have the best of her family's medical facilities, but also for being named after her which increased its popularity, as she is the most famous female Devil in the Underworld. Issei Hyoudou was taken there to be treated after defeating Rizevim Livan Lucifer, due to suffering the negative after-effects of his Diabolos Dragon form.
The original Capital of the Underworld and the Satan territory ruled by the original Lucifer before the four New Satans took office as the second generation Satans.
In the past, the children of the first Satans and their blood relatives lived there and at the Amphitheater, there was a “meeting between young Devils” which was attended by all of the 72 Pillars, but usually served as a way of the Satan descendants to show off their authority among the lower classes of Devils. It is also the place where Sirzechs Gremory defeated and killed Bidleid, thus ending the civil war in the final battle between the Satan and the Rebel army.
There are ruins deep underground that were left by the original Four Great Satans who died, and the only ones who knew of the underground ruins existence were the Six Houses of Lucifer (Lucifuge, Satanachia, Agaliarept, Fleurety, Sargatanas, and Nebiros), as even the Lucifer, Beelzebub, Leviathan, and Asmodeus' bloodlines didn't know about the ruins existence.
The Lucifer Stadium (ルシファー・スタジアム, Rushifā Sutajiamu) a Rating Game stadium in Lucifaad. In the eighth match of the main stage of the "Azazel Cup" tournament, the match between Team White Dragon Emperor of the Morning Star and the Team Journey to the West was held there.
A large city that is located in the Agares territory which is being maintained by the servants of the current Beelzebub. It has a distinctive feature in which it appears to be a large floating island suspended in the sky. A popular tourist resort, it is also the place that controls the flow of the air in the Underworld. The Agreas is a place that has the technology of the Original Satans and contains the essential crystals of the highest quality that is used to create both the Evil Pieces and Brave Saints. In Volume 17, Agreas was taken by Qlippoth. It was finally located by the Vali Team in Volume 20, where Qlippoth had been using the city to both wake Trihexa and create mass-produced Plate Mail armors. By the time of Volume 21, it has been recovered and returned to its original location.
An agricultural town located in the Agares Territory which is said to have the best agricultural products in the Underworld. Sona Sitri's Rating Game school is being built here.
A school building built in Auros that looks like Kuoh Academy. An unusual Rating Game school where even low-to-mid class Devils can attend. It is the first step of Sona's dream, and a school filled with dreams and hopes for the children of the Underworld who lack demonic power. The school was half-destroyed by Euclid Lucifuge, who used a self-destruct technique that was pre-installed in the traitor magicians in the school building who were brought there after being captured when the school was attacked by Qliphoth during the trial enrollment. After that, the reconstruction work is being done with the city of Auros. However, due to the heroic tale of the young Devils of Team DxD protecting the school, the popularity of the school had significantly risen as the applications for trial enrollment has been flooded and reservations for enrollment were full.
The main territory in which the Bael Clan resides in and leads. Contains the Bael Castle in which the members of the main branch family live. The Bael territory is famous for it's natural environments, growing various beautiful flowers and delicious fruits, the most famous being the Bael Apple. The Bael territory and castle would come under attack from Bedeze Abaddon and his peerage during the events of the Evil Dragon War, as he sought to depose the heads of the Bael Clan to hide his own involvement in the King Piece scandal.
The castle of the Bael clan is robust and second to none amongst the various other territories. It is protected by more than fifty barriers cast over it and has boasted never to have been compromised, even during the civil war, until the events of Volume 21. The castle is home to Lord Bael and his family as it is the main residence that serves as the place of ruling. It has a courtyard planted with a revived, beautiful purple flower by the clan's botanist, Magdaran Bael, the second son of Lord Bael. The castle is defended by the Bael's elite guards who patrol the entirety of the castle, always ready to flock to their masters sides and protect them.
The Bael Stadium (バアル・スタジアム, Bāru Sutajiamu) A stadium in the territory of Bael Clan. In the second match of the main stage of the "Azazel Cup" tournament, a match between Team Imperial Purpure and Team Shooting Star was held in the stadium.
The Gremory Clan has a territory that is about the same area of Honshu in Japan. A very rich territory with developed industry. Located within the territory is the Gremory Palace, the home and main building of the Gremory Clan Head.
The place of ruling for the Gremory clan. It has an underground treasure storage which is the size of several Tokyo Domes (1,509.81 sq ft or 2,013.08 sq ft), divided into sections that stores the payments of the Gremory group for their Devil's work, as well as treasures handed down by the Gremory ancestors. All the treasures are ranked and are sorted by types. There is also a huge theatre where the entrance has a luxurious, decorated door and inside, a giant screen with a 1st floor and lights. The theatre is used to entertain guests; to present something to the audience but it is only used once every few years.
Gremory Mansion (Anime only)
The layout of the mansion's outside is a quadrangle with a courtyard in the middle. Outside at the entrance is a fountain with a circular flower bed surround it, with many gardens in the surrounding areas. Inside the mansion, they raise a lot of camels due to them being used in events within areas governed by the clan.
Oppai Dragon Stadium
A stadium specializing in events such as "Oppai Dragon" show performances, which was just built in the castle town of Gremory. At the entrance is a huge statue of Issei in his Scale Mail armor and a huge statue of Rias in the costume of Switch Princess.
In True Volume 2, during the third round of the first round of the "Azazel Cup" main tournament, the teams of Team Red Dragon Emperor of the Blazing Truth and Team Rias Gremory had a match at the stadium. The stadium was fully packed as it hosted the fight between the famous Oppai Dragon and Switch Princess. All the tickets were sold within a a short period of time as the match was highly anticipated. For those who were unable to see the match live, a large number of hyped fans who weren’t able to get into the stadium had gathered around the stadium where large screens were located to watch the live screening of the match.
The place of ruling for the Astaroth clan. In the territory, there is a prestigious noble schools for High-Class Devils lined up in the territory and the promotion examination center is also said to be the most prestigious in the Underworld.
Ajuka Stadium (アジュカ・スタジアム, Ajuka Sutajiamu) is a stadium built in the Astaroth territory in commemoration of Ajuka. The interior corridors were equipped with automatic cleaning robots, and all kinds of facilities were present. The waiting room was also very spacious; as there were no problems with human-like beings entering, and there weren’t any issues with giants entering the room in their original bodies either. In the Azazel Cup qualifiers, a match between Team Red Dragon Emperor of the Blazing Truth and Team Trump Card of Heaven was held in the stadium.
The Dragon mountain is also connected to and a part of the territory of the Gremory Clan. It was given and taken under the care of Tannin alongside his many and various dragons that Tannin took from the Human world. The reason why Tannin took this place was to obtain a certain fruit called Dragon apples in order for his other kin to survive. It was also here where Issei Hyoudou trained himself to enhance his dragon powers and Crom Cruach also lives here due to Tannin taking him under his care.
Fallen Angel Territory
The portion of the Underworld belonging to the Fallen Angels after they fell from Heaven. Comparing the Fallen Angel side territory to the Devil side territory, there are many free areas compared to the number of residents. The residents living in the Fallen Angel sides are the pure Fallen Angels, the races which have a relation to the Fallen Angels, and the half-Fallen Angels born between Fallen Angels and other races.
After the Demonic Beast Riot and the subsequent loss of more Fallen Angels, the Grigori started using the free lands to develop them into a resort area for the factions who made an alliance with the Fallen Angels, as the Grigori have a major plan for building businesses and casinos. Due to the popularization of the idea, the Fallen angels have already received an order from VIP's of different factions that want to have mansions or locations to stay, with the Grigori believing that the venture will turn into a large industry. The idea was conceived due to the Grigori needing to do something about the free areas as well as a means of obtaining money for the Grigori ventures.
The Azazel Stadium (アザゼル・スタジアム, Azazeru Sutajiamu) is a large stadium for the tournament created in the Fallen Angel territory after the Evil Dragon War. A bronze statue of Azazel is erected in front of it. In the Azazel Cup qualifiers, Team Red Dragon Emperor of the Blazing Truth and Team Lightning had a match against each other, and the match between Team Asura and Team Black Satan of Darkness Dragon King was also played there.
The Fafnir Stadium (ファーブニル・スタジアム, Fābuniru Sutajiamu) is a newly built stadium in the Underworld's Fallen Angel territory in honor of The Dragon King; Fafnir, who helped Azazel. In front of the stadium stand statues of Fafnir and Azazel in "Down Fall Dragon Another Armor." In the Azazel Cup qualifiers, Team Rias Gremory and Team White Dragon Emperor of the Morning Star had a Rating Game match.
The Armaros Colosseum (アルマロス・コロシアム, Arumarosu Koroshiamu) is a amphitheater named after Armaros, an executive of Grigori, built in the Fallen Angel territory of the Underworld. On both sides of the main gate is a statue of Armaros that looks just like the real thing. In the Azazel Cup preliminary stage, a match was held there between Team Red Dragon Emperor of the Blazing Truth and Team Sona Sitri.
Other Underworld Domains
Also known as the Realm of Hades in Greek mythology and Depths of Hell. The place where Hades the God of the Dead and the Grim Reapers reside. Located in the lower strata of the Underworld and the place where the souls of the dead are sorted and is also close to Cocytus. The realm of the dead is of the Olympus World; the God from the Greek-faction Hades is in control of it. It isn't as big as the Underworld and as it's the World of the dead, it is a wasteland that no living creature can live in. It also has an ancient Greek shrine as it appears into the depths. It is the place where the Grim Reapers of this World live and where the castle of Hades is located. There is a part in it that is something that looks like a ritual area. Ornaments such as gold are used for the interior and it's so gorgeous that it doesn’t suit being in the Underworld. There is a carving on the wall of the trinity Gods of Olympus – Zeus, Poseidon and Hades and it is carved to stand out. It's also where Vali's great grandmother Lilith is being held captive by Hades.
Purgatory was prepared for the deceased with special circumstances and to purify the spirits and souls who have died. It also the place were those who have died have are judged on if they are going to Heaven or Hell. It was also connected to one of the doors of Heaven like the Third Heaven. This is the place where Cao Cao was able to enter the Third Heaven.
The edge of the Underworld, is the place that it was speculative about the afterlife condition of those who die in original sin without being assigned to the Hell of the Damned and also the burning place. It is also connected to one of the doors of Heaven.
It’s the floor which is one floor above the deepest floor in Hell. It’s said to be the place where those who have evil minds, wicked souls, evil spirits who have committed sins get sent to and punished.
Also known as the Ice Hell, is the deepest part of the Underworld that is connected to the Realm of the Dead. It acts as a prison for powerful and dangerous figures such as Samael and Kokabiel. It is also serves as a home to many rare and dangerous creatures such as the Pale Horse. It’s for those who committed the gravest sins or those who perpetrated betrayals were eternally bound in the cruelest depths of Hell.
An RPG game created by Azazel as a joint project with Ajuka, Sirzechs, and the technicians of the Devil's side. The game uses the Devil's technology the Game Field, to provide an adventure-type experience. It’s an open-field RPG where within the massive field, there are things such as villages, caves, towers, and one becomes a player, who ventures through the area while slaying monsters. It’s an RPG game which can be experienced in first-person, where a person who plays the "Hero" can go on an adventure with their comrades and defeat the evil Dragon King! Participants who play as the hero's comrades can pick from a variety of roles such as Knight, Wizard, Priestess, or Clown, or play as a companion to the Hero and his comrades. A person can also play as an NPC such as a Villager or Blacksmith.
The game is still in development and a member of Grigori is overseeing the project after Azazel was expelled from the project. The game is developed for humans with special abilities who want to fight against mystical beings.
A smartphone game created by Ajuka, to use as a training ground for Rias’ team and Issei’s team.
- The current capital of the Satan territory, Lilith, is a reference to the female demon Lilith from Christian and Hebrew beliefs, mother of monsters.
- Seemingly named for Lucifer's wife, Rizevim's mother.
- Because of the previous Great War, which caused a drastic decrease in both devils and fallen angels, there's abundant untouched regions, in addition to remote areas that are almost unreachable.
- There is a hamburger restaurant chain in the Underworld named Akuma-naldo.
- Malebolge means "evil ditches" and is the name of the eighth circle of Hell in Dante Alighieri's Inferno, part of the Divine Comedy.
- Azazel Quest was named by Azazel himself.
- The Underworld has many unique car models such as a sports car with an exquisite streamlined body constructed from mythril silver, uses demonic energy to run, and reaches 320km per hour (as fast as the Shinkansen); an ordinary sedan that is actually an iron golem that operates as a car; a ghost car possessed by a guardian spirit; a gigantic car that can fit all members of Team [DxD].
- The capital of Lucifaad has a stadium called Lucifer Stadium for the Azazel Cup in honor of Vali Lucifer.