Fifty years ago, Antón's father was El Presidente of Yara. A revolution occurred, and Antón's father was executed right in front of him. As a result, Antón grew up with the view that the island was stolen from his family. He was raised by his mother who made sure her son knew that his father had lost everything he built by those who killed him. When Antón was 13, he was imprisoned and sentenced to fifteen years of hard labor in Yara's tobacco fields. Rumor has it he still has the pruning knife he used as a reminder. In the ensuing decades, Yara experienced great economic decline, affirming Antón's belief that only the Castillo family could save the island. As such, he became El Presidente himself, elected under the promise that he could rebuild Yara into the country it had been fifty years ago. However, he began to run things with an iron fist, and those who spoke out against his methods were taken into forced labor. Economic sanctions were imposed on the country in response, which led to unrest. Responding in turn, Antón tightened his grip on the island.
Antón remains determined to restore Yara to its former glory, with his son, Diego, following in his bloody footsteps. Antón's oppressive actions have resulted in revolution. He is grooming Diego to take his place to succeed him.
His determination is further increased when he developed acute leukemia 13 years prior to Far Cry 6, he was convinced by María Marquessa to have a kid for insurance, he hated kids. But Maria convinced him and Diego was that kid, explained when Anton confronts Clara García and Dani Rojas. but was kept alive through the medicine, Viviro. However, it began to stop working by 2021 and begins to slowly die from leukemia.
When being confronted by Dani Rojas, Antón says goodbye to both Diego and Dani, expressing his wishful thinking that Diego will be protected in the bleak future of Yara after he is gone, while Dani promised so, Antón discarded Dani 's promise as lies, and abruptly shot Diego in a twisted form of mercy killing, likely because he doesn't want Diego to suffer. Antón also immediately slit his own throat with his tobacco pruning blade and died alongside his son.
If Dani takes the boat to leave Yara and live in the US, a news report can be heard about Antón, claiming that his special forces killed Clara Garcia and "war is ending in Yara." Whether that be the truth or not is left unverified due to Castillo's regime tight censorship. Since the report was heard 3 months after Dani left Yara, all that can be known is Antón managed to live on for 3 more months and still being the leader of Yara with his regime still stand. It's unknown what would happen to him afterward, such as whether he finds a way to continue living or inevitably die, leaving Diego as the next leader of Yara.
- Antón's actor, Giancarlo Esposito, has worked with Vaas Montenegro's actor, Michael Mando, in a popular show Better Call Saul.
- Anton’s surname translates in English to “Castle”.
- Although he had a nephew, this would mean he has a brother, yet he was never brought up in any conversations nor was he mentioned anywhere else.
- Despite having a surname that sounds similar to "Castro", he is primarily based on Fulgencio Batista, the former dictator of Cuba. Both men oversaw a brutal regime of government repression, censorship and corruption. Like Batista, Castillo is locked in a civil war for control of his island nation. He is also not above doing business with foreign investors such as Sean McKay, despite severe economic sanctions. Unlike Batista, he does not flee his country when the war turns against him, instead preferring to kill his own son and himself rather than suffer at the hands of the rebels.
- He is the second antagonist in the series that is a military dictator, the first being Pagan Min.
- Unlike Min, Castillo is a native of his game's setting, as well as conservative in his attire and mannerisms. He also came to power through free elections rather than deception and violence. Furthermore, his brutality is somewhat justified as he is trying to fix the mess left behind by the 67' Revolution that caused the downfall of Yara's economy.