Four Great Satans

The Four Great Satans (Lucifer, Leviathan, Beelzebub, and Asmodeus) were the original rulers of the Underworld and leaders of the Devils.

Summary
At some point in the past, the four original Satans created the Demonic Swords, and led the Devils against God and the Angels in Heaven as well as Azazel and the Fallen Angels in the Great War, the latter who retreated prior. The Four Satans eventually died in the Great War.

After their death in the Great War, the descendants of the Four Great Satans intended to carry on their legacy and finish the Great War but were opposed by a certain group of Devils which caused a huge conflict between the Devils. Following the defeat of the descendants who were forced to retreat to the back part of the Underworld, their names became titles for the new supreme rulers of the Devils.

The current Satans are Sirzechs Lucifer (Gremory), Serafall Leviathan (Sitri), Ajuka Beelzebub (Astaroth), and Falbium Asmodeus (Glasya-Labolas), four Devils who were born with insane power, equivalent or superior to the original four but do not carry the blood of the original Satans.

Three of the descendants of the original Satans – Katerea Leviathan, Shalba Beelzebub, and Creuserey Asmodeus – have allied with the Khaos Brigade's Old Satan Faction, while Vali Lucifer has formed his own team in the Khaos Brigade. As of Volume 11, Vali is the only survivor among the descendants of the original Satans as the others were killed in battle.

Trivia

 * All four of the current Satans have legendary creatures in their group/peerage.