Four Emperors

The Four Emperors (四皇, Yonkō) is a group that appears in the One Piece series. They are the four most notorious and most powerful pirate captains in the world, but are neither allies nor enemies of one another, preferring to remain autonomous under most circumstances. These four individually reside within the second half of the Grand Line (known as the "New World"), exerting impressive influence and control over dozens of other pirate crews and self-governing islands.

In the decisive Battle of Marineford, Whitebeard, one of the Four Emperors, met his end towards the climax of the Whitebeard War. Blackbeard, his killer, subsequently usurped his position. Shanks, another member of the Four Emperors, arbitrated a ceasefire to end the aforementioned war.

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 * —About the Four Emperors.

Abilities and Powers
"A threat...a demand...when issued by one with absolute, overwhelming power becomes simply inevitable fate...after all, who could possibly oppose it? That is the existence known as the Four Emperors! And this is what it means to be driven to your very wit's end...!"
 * —Pekoms on the scope of the Four Emperors' power.

As an entity, the Four Emperors are one of the Three Great Powers of the world, with the others being the Seven Warlords of the Sea and the Navy. Their strength and influence are such that they live quite literally as though they are emperors, doing mostly as they please.

Individually, they are considered to be the most powerful pirates in the world, with devastatingly powerful and versatile Devil Fruit abilities, immense physical strength, endurance, and durability, and/or sheer mastery of Haki. Whitebeard, the first Emperor to display his full fighting prowess, was even in his old age considered to be the Strongest Man in the World, possessed the powers of the Tremor-Tremor Fruit, the Devil Fruit considered to be the strongest within that of the Paramythia class, and had mastery of all three types of Haki. He was eventually killed in the Battle of Navyford after receiving nearly 500 grievous wounds, and even then, died standing as a testament to his tenacity and inhuman strength. Blackbeard, who killed the former with the aid of his crew, then gained the powers of Whitebeard's fruit through unknown means, thus becoming the first known individual to have acquired multiple Devil Fruit abilities; over the course of the following year, with the aid of his newfound powers, he would usurp Whitebeard's former position as an Emperor.

Though powerful in their own right, much of the Four Emperors' martial strength can be attributed to their elite and abundant crews, as well as to their close alliances with other pirate captains. Whitebeard's crew amounted to over 1600 men and he also had 43 subordinate New World pirate crews to aid him in his efforts to rescue Ace, each headed by an infamous pirate captain. Some of these subordinate captains were very powerful in their own right, as seen with Little Oars Jr.'s impact as a key player for the Whitebeard Pirates during the Battle of Navyford.

Due to the sheer size of their crews, most of the Four Emperors utilize several elite commanders to lead their forces; Whitebeard originally had sixteen division commanders (each leading 100 men), Kaido has his three Disasters, Big Mam has her Three Sweet Commanders (originally Four), and Blackbeard, who originally only had a small crew of under ten men prior to his becoming an Emperor and expanding his crew size drastically, later has it subdivided through his Ten Titanic Captains, some of whom were members of his original crew. As seen with top Whitebeard commanders' Marco, Ace, Jozu, and Vista's skirmishes with the Seven Warlords and Navy Admirals during the Battle of Navyford, these top officers are seen to be able to contend with the elites of the other two Great Powers. Due to their exposure and feats as executive officers for the Four Emperors, the commanders are regarded as a huge threat by the Navy, second only to their Four Emperor captains. Thus far, the four highest known active bounties all belong to Emperor commanders (Cracker, Smoothie, and Katakuri of the Big Mam Pirates at 860,000,000 berries, 932,000,000 berries and 1,057,000,000 berries respectively, and Jack of the Beasts Pirates at 1,000,000,000 berries) while interestingly, none of the Emperor themselves have had their bounties revealed.

Because of their power, the Four Emperors can declare chosen locations as their own; the mere declaration is often enough to compel others, both Navy and pirates alike, to acknowledge and respect the Emperor's authority; when Whitebeard declared the crime-ridden Mermen Island to be under his control, he immediately ended all pirate attacks on the island as well as its slave trade.

Accordingly, they each have a large territory that they govern within the New World. The Four Emperors provide protection to all who reside within their territories, keeping the borders safe from any faction that may wish to invade them. Big Mam's territory, Totto Land, is heavily protected by scouting ships and by watchtowers called Tartes that dot the coastlines of each of her islands, both prepared to inspect and potentially shoot down any ships not affiliated with her crew. She also has territorial sea slugs that patrol the waters, warning would-be intruders that they are entering her territory. Finally, Big Mam has 34 ministers as part of her administration, one to run the affairs of each of her territory's subsidiary islands.

It is only with the combined efforts of the Navy and the Sven Warlords of the Sea, as well as the distrust amongst them, that keeps their power in check. During the Battle of Navyford, the Navy and Seven Warlords needed to fight together just to engage one of the Emperor, Whitebeard, his crew, and their allies. The arrival of a second Emperor, Shanks, immediately brought an end to hostilities, showing the power and influence they have without even needing to engage in combat.

The Four Emperors themselves are not allied together as a coalition compared to the Seven Warlords of the Sea, and follow their separate agendas. Nevertheless, most of the Four Emperors still seem to have the intention of becoming the King of the Pirates and finding One Piece, with former Emperor Whitebeard being an exception. The possibility of two or more of the Four Emperors forming an alliance was enough of a threat to cause the World Government to panic, seen when it unsuccessfully attempted to prevent a meeting between Shanks and Whitebeard. The World Government feared that the two Emperors would unify, creating a much more imposing threat that would disrupt the balance between the Great Powers. A war between two of the Four Emperors is considered a terrifying crisis, as Shanks' interception of Kaido's advancement on Whitebeard had taken the Navy by shock and awe, putting the World Government in a "cold sweat" as stated by one of the Navy.

They can motivate others to partake in a life of piracy; Shanks personally inspired Luffy, and the death of Whitebeard inspired many pirates to travel to the Grand Line.

After the timeskip Trafalgar Law cited that there are only two methods of surviving in the New World, and that is to be protected under the umbrella of the Emperor's dominion and become their ally or to constantly oppose their authority. At least Teech and Kaido are both gaining influence and strength in the form of amassing Curséd Fruit powers, both in their own unorthodox methods. Big Mam intends to increase her crew's power by forming an alliance with the legendary Germa 66 and gain access to their advanced technology.

Because of their immense power, it is necessary for factions aiming to oppose them to first strike an alliance with other factions in order to bring the Four Emperors down. However, even with multiple alliances amongst powerful pirates, the chances of defeating an Emperor are still extremely low; when the Straw Hat Pirates and the Heart Pirates formed an alliance to defeat Kaido, Law informed Luffy that he believed their chance of success was only 30%.

Emperor Charlotte Lingling and Kaido both have a single Road Ponecliff that can, with all four Road Ponecliffs deciphered, lead to Raftel's location.

History
Whitebeard was active on the seas during Gol D. Roger's voyage across the Grand Line; he was said to be one of the few people who could rival Roger, as well as the man closest to One Piece after Roger's death. However, he had no intention of finding the treasure.

Big Mom was also on the seas during Roger's voyage and even encountered him when he managed to acquire and read her Ponecliffs, allowing Roger to beat her to Raftel.

Throughout his life, Kaido was defeated seven times by the Navy and other Four Emperors. However, all of their attempts to execute him were unsuccessful.

Some of the Seven Warlords of the Sea have fought the Four Emperors in the past; Shanks and Dracule Mihawk frequently dueled in their younger days, Gecko Moria fought Kaido, and Crocodile fought Whitebeard.

Twelve years ago, Shanks visited Luffy's hometown. It is unknown if the title of Emperor existed at that point in time or if he was one at the time as well.

About four years ago, Kaido formed a partnership with Don Quixote Doflamingo and Caesar Clown so that the two would give him Artificial Devil Fruits known as SMILEs, which he used to create an army of Devil Fruit users known as Gifters.

All of the Four Emperors seem to have strong fleets, including huge ships and elite crewmen. At some point, they all traveled to the New World where they are currently locked in a stalemate, unable to progress any further into the Grand Line. This is a product of the combined efforts of the Navy and the Seven Warlords of the Sea, as well as the presence of the other Emperors. A particular reason for their inability to reach Raftel is the fact that one needs all four Road Ponecliffs to determine its location; one is possessed by Kaido, one possessed by Big Mam, one is located on Zou, guarded by the Minks and the last one is in an unknown location.