The Four Emperors are four pirates considered to be the most notorious and powerful captains in the world. Currently, these four are recognized as Shanks, Marshall D. Teach(Blackbeard), Monkey D. Luffy, and Buggy, with known predecessors being Edward Newgate(Whitebeard), Charlotte Linlin(Big Mom), and Kaidou.
Historically, the Emperors have dominated the second half of the Grand Line (the “New World”), captaining powerful subordinates and massive fleets while exerting influence and control over dozens of separate pirate crews and even full-fledged nations. As such, the World Government views them collectively as one of the Three Great Powers underpinning world stability. However, no formal system supports them; each Emperor works as an independent force, and may oppose or align with whomever they see fit.
With the rise of the Worst Generation, the Emperors underwent much upheaval, beginning with Teach’s murder of Newgate during Summit War of Marineford[8] and usurpation of his position. Two years after the war, Kaidou and Linlin formed an unprecedented two-Emperor alliance, only to be toppled by the Ninja-Pirate-Mink-Samurai Alliance in the Raid on Onigashima. Subsequently, Luffy and Buggy were declared new Emperors, the former for defeating Kaidou in combat and the latter for his unwitting “leadership” of the infamous Cross Guild.
As an entity, the Four Emperors are one of the Three Great Powers of the world, the others being the Marines and the Seven Warlords of the Sea (the latter of which were abolished and replaced with the Seraphim). Their strength and influence are such that they live quite literally as though they are sovereigns, doing mostly as they please as the “Emperors of the Sea”.
Individually, the Emperors are usually considered to be the most powerful pirates in the world, with devastatingly powerful and versatile Devil Fruit abilities, immense physical prowess, a sheer mastery of Haki, or, most often, a combination of all three. Their individual bounties are among the highest in the world, with the lowest being 3,000,000,000 and the highest (formerly) over 5,000,000,000. The only known pirates with comparable bounties to the Four Emperors are their greatest known rivals: The captain of the Heart Pirates, “Surgeon of Death” Trafalgar Law and the captain of the Kid Pirates, Eustass “Captain” Kid are two of Straw Hat Luffy’s biggest rivals among the Worst Generation, having the same bounty as him; “Hawk Eyes” Dracule Mihawk was Red-Haired Shanks’ old swordsman rival before the latter lost an arm; and the Pirate King and captain of the Roger Pirates, Gol D. Roger, was Whitebeard’s rival back when he was alive.
In addition, all known former Emperors (Whitebeard, Kaidou, and Big Mom) were once members of the legendary Rocks Pirates, considered the world’s strongest pirate crew of their time. Also, two of the current Emperors (Shanks and Buggy) are former members of the Roger Pirates under the service of the late Pirate King, and the other two (Teach and Luffy) are carriers of the Will of D.
During a Marine briefing, it was stated that an alliance between two of the Four Emperors could lead to the formation of the strongest pirate crew in recorded history, and that the collective bounty of such an organization’s captains alone would easily dwarf that of even the Pirate King himself. During the Raid on Onigashima, Luffy, Zoro, Kid, Killer, and Law worked desperately to separate Kaidou and Big Mom from each other and keep them separated due to how dangerous it was to face the two Emperors at the same time.
