Khaos Brigade

The Chaos Brigade (禍の団（カオス・ブリゲード） Kaosu Burigēdo), also known as the Army of Disaster, is an organization in High School DxD consisting of humans who are descendants of legendary/mythological heroes. They are the main antagonists of the light novels from the Birth of the Breast Dragon Emperor arc to the Heroic Oppai Dragon arc.

History
The Chaos Brigade was created by Ophis, one of the two Divine Dragons, with the sole purpose of removing the Great Red, another Divine Dragon and the most powerful Dragon in existence, out of the Dimensional Gap. However, she was betrayed when Sousou, the leader of the Hero Faction, sided with Hades, the God from the Realm of the Dead, and stole most of her powers under the intention of creating another Ophis, resulting in the latter being in a powerless state.

Vali Team
THe Vali Team (ヴァーリチーム VarĪ Chīmu) is the first faction of the Chaos Brigade led by Vali Lucifer, the descendant of Lucifer and the keeper of Albion, the White Dragon Emperor and Vanishing Dragon and the arch-rival of Ddraig, the Red Dragon Emperor. Known members of the Vali Team include Arthur Pendragon and Le Fay Pendragon, the Pendragons who are the descendants of King Arthur and Morgan le Fay; Bikou, the descendant of the first Monkey King, Son Goku; Kuroka, Koneko's older sister and an exiled Devil; Fenrir, a giant wolf who is the son of Loki; and Gogmagog, a golem from English folklore.

Old Satan Faction
The Old Satan Faction (旧魔王派 KyūmaŌ-ha) is the second faction of the Chaos Brigade consisting of Devils who are descendants of the original Satans: Beelzebub, Lucifer, Asmodeus, and Leviathan. They are the only group of Devils who resist 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 system, and they seek to change it by overthrowing the current Satans. The leaders of the Old Satan Faction are Cattleya Leviathan, Cluzerei Asmodeus, and Shalba Beelzebub.

All three members of the Old Satan Faction were defeated in Volume 11 of the light novels and its remaining members terminated by Ajuka in Volume 12, making their faction the first of the Brigade to be defeated.

Hero Faction
The Hero Faction (英雄派 Eiyū-ha) is the third faction of the Chaos Brigade led by Sousou, the descendant of Sousou from the Chinese novel Romance of the Three Kingdoms and the one who betrayed Ophis. It is a faction of the Chaos Brigade that is allied with Hades, the God from the Realm of the Dead, and it is also the most dangerous faction of the Chaos Brigade due to its members being Sacred Gear, Holy/Demon Sword, and Longinus wielders.

Members of the Hero Faction include Georg, the descendant of Johann Georg Faust, the human who contracted with the legendary Devil Mephistopheles; Siegfried, the descendant of the dragon-slaying hero in Nibelungenlied; Joan, the descendant of the Maiden of Orleans, Joan of Arc; Heracles, the descendant of the Greek mythological hero Heracles; and Leonardo. Freed Sellzen later joins the Hero Faction and has his body modified to that of a chimera before he was killed off by Yuto Kiba.

The Hero Faction was finally defeated in Volume 12 when Indra sends most of its members (Sousou, Leonardo and Georg) to the Realm of the Dead, taking all of their Longinus from them. The fate of the remaining members (Joan and Heracles) remain unknown, while Siegfried was the only member of the Hero Faction who died in battle.

Trivia

 * Leonardo and Kuroka are the only known members of the Chaos Brigade to not originate from heroes.