At least some content in this article is derived from information featured in Fantastic Beasts: The Crimes of Grindelwald. As such, spoilers will be present within the article.
Antonio was a baby Chupacabra chained to Gellert Grindelwald's chair in his cell during his brief imprisonment at the Magical Congress of the United States of America in 1926-1927. Most notably, it participated in Gellert Grindelwald's escape.
Shortly before Grindelwald's attempted extradition to Europe, under escort by several Aurors and Rudolph Spielman (the International Confederation of Wizards's Head of Incarceration) Grindelwald managed to switch places with MACUSA official Abernathy by use of the Polyjuice Potion. After the high-security flying carriage set off from the Woolworth Building, the real Grindelwald Apparated onto the carriage, eliminated all the Aurors, and destroyed Rudolph Spielman's wand — panicking, Spielman opened the box that had been handed to him supposedly containing Grindelwald's wand, but Antonio sprung from inside and sank its fangs deep into his neck.
Once Grindelwald clambered inside the carriage, he ripped the Chupacabra off Spielman and rubbed him affectionately; without further warning, Grindelwald looked at the creature with distaste and judged it to be "So needy", throwing it out the door of the flying carriage, which would have resulted in its certain death.
- Fantastic Beasts: The Crimes of Grindelwald - The Original Screenplay (First appearance)
- Fantastic Beasts: The Crimes of Grindelwald