TV-Series
Description
Caesar Crown, also known by his scientific alias "Master," is a prominent antagonist first encountered during the events on Punk Hazard. He is a former colleague of the renowned scientist Vegapunk and is recognized as a leading authority on chemical weapons of mass destruction, with a bounty of 300,000,000 berries on his head.

In terms of background, Caesar was originally a member of the illegal research group MADS, working alongside other brilliant minds like Vegapunk and Vinsmoke Judge. He later followed Vegapunk into the World Government's scientific unit, where he was ranked second in ability. His career took a catastrophic turn when he detonated a chemical weapon on the island of Punk Hazard. The explosion permanently shattered the island's climate, turning one half into a burning inferno and the other into a frozen wasteland, and killed or crippled most of its inhabitants. After being arrested for this incident, Caesar escaped from a prison ship and returned to the ruined Punk Hazard, where he began conducting forbidden research in secret. There, he entered into a partnership with Donquixote Doflamingo to produce SAD, a crucial component for manufacturing artificial Zoan-type Devil Fruits known as SMILE. He also embezzled significant funds from the Emperor Big Mom under the pretense of continuing his stalled research into human gigantification, using the money instead for a hedonistic lifestyle.

Caesar's personality is defined by a profound and destructive egomania. He is, in the words of Marine Vice Admiral Smoker, a "very crazy bastard," taking genuine delight in causing harm and suffering with no trace of remorse. His cruelty is demonstrated through acts such as kidnapping children and addicting them to lethal, experimental drugs to ensure their compliance, and callously using his own loyal subordinates as test subjects for his deadly gas weapons. Despite his monstrous behavior, Caesar is also a pathological liar and a skilled actor, often feigning concern and shedding crocodile tears to manipulate the blind trust of his followers, who once viewed him as a savior. He harbors an intense grudge and an inferiority complex towards his former colleague Vegapunk, flying into a rage whenever the man's superior intellect is praised. For all his arrogance and sadism, Caesar is fundamentally a coward. He becomes whiny, panicked, and utterly subservient when his own life is threatened, frequently begging for mercy or desperately seeking protection from more powerful figures. His distinctive laugh is "Shurorororo".

His notable abilities stem from his consumption of the Gas-Gas Fruit, a Logia-type Devil Fruit. This power allows Caesar to create, control, and transform his body into various forms of gas. He can use this ability to fly by propelling himself, create explosive gas clouds, generate poisonous compounds to incapacitate or kill opponents, and even remove the oxygen from the air in a large area, causing anyone within it to suffocate. He is also a brilliant scientist, skilled in chemistry, pharmacology, and weapon development, creating terrifying weapons like the deadly poison gas Shinokuni and the explosive KX Launchers. He typically remains in a partially gaseous state at all times, giving his body a misty, ethereal appearance.

Regarding his role in the story, Caesar serves as the main antagonist of the Punk Hazard arc, where he is defeated by the Straw Hat and Heart Pirate alliance. After his defeat, his heart is taken by Trafalgar Law, forcing him into a hostage situation and cooperation with the victors. He is later forcibly retrieved by Big Mom's crew and brought to her territory of Totto Land. In a desperate bid for freedom and survival, he allies with the Fire Tank Pirates and the Straw Hats to participate in a failed assassination attempt on Big Mom.

Key relationships define much of his journey. He is a bitter rival of Vegapunk, an associate of the sinister underworld broker Donquixote Doflamingo, who provided him protection, and an unwilling pawn of the Emperors Kaidou and Big Mom, both of whom desired his research. He also has a manipulative and cruel relationship with his former subordinates, like Brownbeard, whom he betrayed without hesitation, and his assistant Monet, whose death he inadvertently caused. After losing his protection from Doflamingo and escaping the chaos of Big Mom's territory, Caesar ultimately aligned himself with Vinsmoke Judge, his former colleague from MADS, and together they formed a new research organization called NEO MADS.

His character shows a consistent arc of self-serving survival. From a powerful, confident tyrant ruling over Punk Hazard, he is reduced to a terrified, manipulated prisoner and then to a reluctant, scheming ally. Even when given his freedom, he does not reform but instead returns to what he knows best: unethical scientific research, highlighting that at his core, he remains an unrepentant and selfish individual focused solely on his own ambitions and preservation.