Trebol is a member of the Donquixote Pirates. He is one of the top executive officers within the Donquixote Pirates. He is one of the major antagonists in the Dressrosa Arc in One Piece.
Trebol is loyal to Donquixote Doflamingo and is willing to help him become the Pirate King. From a young age, Trebol was fascinated by Doflamingo and would encourage him to commit violence and harm others in his path towards becoming the Pirate King. Trebol is also loyal to his crew as well. With people he is familiar with, Trebol would often get close them in person. He also shows that he is willing to get throw things and attack people when he is angry such as personally attacking Law when the latter insulted them. Trebol can get personally emotional to the point that he would disobey an order from Doflamingo and attack his enemy.
When Trebol was a teenager, he met Doflamingo in North Blue along with Vergo, Diamante, and Pica. Fascinated by the former Celestial Dragon using Haoshoku Haki, Trebol told him that was a sign that he was chosen. Allying himself with Doflamingo, Trebol armed Doflamingo with a gun and gave him the String String Fruit, telling him to take revenge on those who wronged him. Doflamingo would use the gun to murder his father and attempt to get back into Mariejois and fail. After he returned, Trebol would support Doflamingo and encourage him to commit extreme violence by attacking anyone who would insult him.
Trebol would also help Law when he was a member of the Donquixote Pirates and was also present on Minion Island helping Doflamingo look for the Op Op Fruit. Years later, Trebol would assist Doflamingo and the Donquixote Pirates take over Dressrosa by helping to frame King Riku for many murders and playing a role in taking over the country. Trebol would oversee the labor of Doflamingo underground factory and would be there to protect and watch after Sugar as she turns people into toys to be slaves.
Trebol first appears in the palace where he meets with Doflamingo, Diamante, and Pica about the Fire-Fire Fruit and the Corrida Colosseum. Trebol later appears watching the underground workers and keeping an eye out for spies who could be there. At one point, Trebol was enraged over being tricked by a potential spy and throws a boat destroying the officer tower. Usopp was able to incapacitate Sugar causing everyone and everything that was turned into toys to revert back to their original form. Trebol tries to handle the chaotic situation.
As many battles and the chaotic situation escalates with Doflamingo summoning the Bird Cage on the island, Trebol joins Doflamingo at the top of the palace. He was present when Bellamy tried to talk to Doflamingo about the latter’s treachery. When Law and Luffy tries to fight against the duo, they were able to successfully attack him and Doflamingo. However, as the fight progress, Trebol and Doflamingo had the upper-hand against Luffy and Law. Doflamingo manages to kills Law after the latter refused to help him.
When it turns out that Law was not dead, Trebol and Doflamingo were caught off guard by Law and Luffy's attack. He was in awe at Luffy using Haoshoku Haki to clash with Doflamingo. After regaining his wits, he then tells the duo about how monstrous and dangerous Doflamingo is.
During the fight, Law manages to trick Trebol by making the latter very emotional with his comments. Doflamingo advises Trebol to not fall for Law's moves, as he is tricking him but is ignored. Law then severely attacks him with his severed sword arm, causing him to shed his slime coat. In a last ditch effort, Trebol attempted a suicide-bombing by snaring Law in his slime and blowing himself up along with Law. The attempt failed but everyone managed to survive Trebol's suicide attack. Trebol survived the attack but was left incapacitated from his move and with Doflamingo's defeat, the marines arrested all members of the Donquixote Pirates except for Baby 5. Trebol and the other Donquixote Pirate members were all escorted to Impel Down.