The Militant Faction, also known as Thanatos' Grim Reapers, is a group of Grim Reapers lead by the oldest and most powerful Ultimate-Class Grim Reaper: Thanatos. During Erebus' attack on Kyoto, the Conservative Faction and other Anti-Hades Grim Reaper factions were contacted by the other mythological factions to discuss the post-war treatment of the Netherworld as the other factions viewed the attack as a declaration of war and the Three Factions ordered Team DxD to destroy Hades and his patrons. In Volume 24, Team DxD contacted Orcus to find information about why Thanatos was targeting Koneko Toujou. Unlike the Progressive Faction, the Conservative Faction doesn't listen to Hades' commands and adopts a wait and see approach in dealing with things, with the Conservative Faction having a amicable relationship with the other mythological faction, like the Three Factions. The Conservative Faction, also known as the Moderate Faction, is a group of Grim Reapers lead by the Ultimate-Class Grim Reaper Orcus. In Volume 24, Hades' Grim Reapers assisted the newly created Artificial Devils in attacking the various territories of the other mythological factions. In Volume 23, Hades and his Grim Reapers discovered the Mother of all Devils Lilith in Cocytus at Rizevim Livan Lucifer's research facility, as Hades ordered his Grim Reapers to contact the other Gods of Hell as he prepared to go to war against the other mythological factions. After the crisis in the Underworld was concluded, the majority of the Grim Reapers at Hades' temple were frozen by Dulio Gesualdo's Longinus Zenith Tempest. Pluto reappeared after Issei returned from the Dimensional Gap in order to try to obtain Ophis, though he was challenged to a fight by Vali Lucifer as Vali defeated and killed him. As the Annihilation Maker Anti Monsters rampaged through the Underworld, Hades wanted to interfere but was prevented by Sirzechs Lucifer as the Grim Reapers at Hades' temple were attacked by the members of the Vali Team.

In Volume 11, during the Demonic Beast Riot, the Executive-class Grim Reaper Pluto lead them into battle as they assisted the Hero Faction in attacking Azazel and the Occult Research Club, due to being ordered by Hades to seize and deliver Ophis to him after she was rendered finite, though the Grim Reapers sent were defeated by the Occult Research Club. The Progressive Faction, also known as Hades' Grim Reapers, is a group of Grim Reapers that follow the orders and commands of the Greek God of the Dead Hades. Ultimate-Class Grim Reapers are noted to be very powerful with the legendary Grim Reaper Pluto fighting on par with Azazel in his Down Fall Dragon Another Armor and the most powerful Grim Reaper Thanatos, being able to overwhelm Issei Hyoudou in his Cardinal Crimson Promotion and even dodging his attacks in Diabolos Dragon, as it is stated that his power is comparable to that of Gods. Due to their power and ancient nature, each holds significant power in the Netherworld as they command their own portion of the Netherworld.

Ultimate-Class Grim Reapers (究極クラスの死神, Kyūkyoku Kurasu no Shinigami) also known as Executive-Class Grim Reapers, are the highest level of Grim Reapers all Grim Reapers.

Behind the gates, a vortex of black aura can be seen. They have sculptures of skulls in different places.

Grim Reapers can travel through their special gates. Grim Reapers also wield a Death Scythe, which will shorten the lifespan of anyone slashed by it with a special type of curse. Grim Reapers can use teleportation by dispersing their bodies, that leaves behind a black afterimage and duplicating themselves to attack and confuse their opponents. The strength of Grim Reapers varies depending on their class, with Low-Class Grim Reapers being stronger than the average Middle-Class Devil. Grim Reapers with darker robes indicates to their higher ranks. It should be noted that Grim Reapers' ranks depend on the darkness of their robes they wear. Little is known about the appearance of Grim Reapers as they are always dressed in dark robes decorated with ornaments which vary depending on the individual, though from glimpses they appear to have skeletal bodies.

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