Old Satan Faction

The Old Satan Faction (旧魔王派 KyūmaŌ-ha) is the largest faction of the Khaos Brigade, consisting of Devils who support the ideals of the original Satans, Beelzebub, Lucifer, Asmodeus, and Leviathan, and allied themselves with their descendants.

Summary
The Old Satan Faction was indirectly formed when a group of Devils decided to continue the Great War and to fufill the Original Satans's ambition of world domination while another group of Devils was against it, resulting in a Civil War among Devils, with the victor being the new Government of the Devil side of the Underworld, while the losers where forced to go into hiding and the original Four Great Satans became known as the Old Satans.

Even after being defeated by the new Devil government, the Old Satan Faction remains active and continues to cause trouble on the Devil side.

The Old Satan Faction is the only group of Devils who resisted using the Evil Pieces, as they believe them to be a disgrace to Devils because they reincarnate Humans and other races into Devils. They are also against the Devils' current political system and seek to change it by overthrowing the current Satans.

Prior to the main story, the Old Satan Faction pledged allegiance to Ophis and became the largest faction among the many factions of Khaos Brigade. They eventually reemerged as part of Khaos Brigade, and one of its leaders, Katarea Leviathan, led the attack at the peace conference of the Three Factions, attempting to kill the leaders of the Three Factions, but was killed by Azazel instead.

The Old Satan Faction eventually launched another large-scale attack on the Underworld with the help of Diodora Astaroth. However, like their previous attempt, it was thwarted by the leaders of the Three Factions along with the allied forces from other myths, resulting in the loss of another of their leaders, Creuserey Asmodeus, while another, Shalba Beelzebub, was heavily injured.

Following the failed attempt during the Rating Game tournament, the Old Satan Faction formed a truce with the Hero Faction. After the Hero Faction betrayed Ophis, Shalba, who had gone insane by then, forced Leonardo into a Balance Breaker state in an attempt to destroy the Underworld by generating powerful antimonsters. He was then killed by Issei.

The remaining top members of the Old Satan Faction and Siegfried then approached Ajuka Beelzebub during the crisis of the Underworld, offering him a place in the Khaos Brigade, while other members participated in riots in the Underworld, taking advantage of the chaos. However their offer was rejected by Ajuka and they were swiftly terminated, while a great deal of their members were defeated. With the third defeat, the Old Satan Faction lost the majority of its forces and was forced into hiding, unable to take any further action.

Members
All the leaders of the Old Satan Faction were killed and the majority of its forces were terminated by Ajuka Beelzebub in Volume 12, further weakening their faction to the point of them being incapable of taking any further actions.