Caesar Clown

Caesar Clown, who was referred to as "Master" by his subordinates, is a demented scientist, a former colleague of Vegapunk, the main antagonist of the Punk Hazard Arc, and the first main antagonist the Straw Hats face in the New World. He is the leading expert on chemical weapons of mass destruction and has a bounty of 300,000,000 Beli on his head. Caesar has authority over all the former test subjects on the island as he saved them from the gas, and he uses their blind-trust to manipulate them. However, after Caesar revealed that he does not care about his subordinates, he lost their faith. In direct combat, Caesar has also proven to be a very powerful fighter, using his Devil Fruit abilities to quickly maneuver out of dangerous situations and being durable enough to take several Haki-imbued Gear Second strikes from Luffy, only to emerge relatively unharmed.

Master Caesar

His durability extends to being seemingly unfazed by either the boiling hot or the sub-zero temperatures which compose the "Burning Lands" and the "Ice Lands" zones on Punk Hazard respectively. He withstood a blow from Luffy that left a big dent in his face and still retained consciousness. He is also very stealthy, being able to administer a muscle relaxant to Brownbeard without the latter noticing. Caesar also has the power to combine with Shinokuni and become stronger. After this transformation, Caesar can petrify anyone he touches. Capone Bege acknowledged Caesar's potential and believed that his assistance would be vital in his plot to assassinate Big Mom. Caesar is also physically strong, able to easily carry around a large and tall mirror which the Straw Hats and the Fire Tank Pirates would use to escape. Caesar also assured his confidence in carrying Brûlée, who is a very tall woman while bringing along the mirror. Caesar has a strong will being able to withstand a burst of Big Mom's Haoshoku Haki. Luffy later caused Big Mom to start screaming and Caesar watched in anticipation as Bege, Vito, and Gotty fired their KX Launchers at her. However, Big Mom's scream caused the rockets to detonate before they reached her. With the assassination attempt a failure, Caesar quickly grabbed the escape mirror and flew into the venue while expressing dismay that Big Mom destroyed his weapons. However, before the alliance could escape into the mirror, Big Mom's scream shattered it.

Gastino

With nowhere to run, Caesar and his allies found themselves surrounded by the Big Mom Pirates, who were given earplugs by Charlotte Katakuri. Bege then transformed into a fortress and instructed the alliance members to get inside. As Caesar fled towards the fortress, Katakuri grabbed Brûlée off his back. After all the alliance members and the Vinsmoke Family successfully retreated inside the fortress, Bege went on to explain about the dire situation they were in. Caesar replied that the failure of the KX Launchers were not his fault, but he was interrupted when the fortress was under attack by a furious Big Mom. As Big Mom continued her onslaught, Bege decided to try turning back into human form and having Caesar fly him away from the venue. Caesar heavily disagreed, and the two argued, before the Vinsmoke Family decided to fight Big Mom in order to provide an opening for them to escape. Bege then squeezed Caesar's heart to get him to go with the plan, and he turned back into his human form as Caesar flew him away from the venue. As Caesar fled with Bege, Perospero blocked his path with a candy wall. Ichiji, Niji, and Yonji combined their attacks to destroy the candy wall, allowing Caesar to path through. When Caesar was close to escaping the venue, Katakuri stood in his way, but Ichiji attacked the Sweet Commander, enabling Caesar to continue. However, Caesar's escape was hindered once again by Brûlée, who was eager to pay the alliance back for using her. As Caesar looked back, he fell into despair upon seeing Luffy, Sanji, and the Vinsmoke Family overwhelmed. However, the Tamatebako dropped to the base of the Whole Cake Chateau and the bomb inside the chest exploded, causing the castle to collapse. While the castle fell, Caesar carried Bege far away from the chateau to the northwestern part of Whole Cake Island. After Bege ended his alliance with Luffy's group, he gave Caesar his heart back. With his heart back in his possession, Caesar happily left them behind.