Marcus Antonius (83 BCE – 30 BCE), commonly referred to in English as Marc Anthony or Mark Antony, was a Roman politician and general. A supporter and loyal friend of Gaius Julius Caesar, he formed a political alliance with Octavian after Caesar's assassination.
In 44 BCE while in Rome, Antonius approached Aya, the Mentor of the Hidden Ones. He introduced himself to her and explained they had a mutual friend in Cleopatra, who held Aya in high regard. Aya refuted that Cleopatra held only herself in high regard, like many leaders in the world. Antonius explained that leaders, like Caesar himself, had to do what it takes to ensure their people survive, though Aya disagreed, believing that a leader should never sacrifice their own people.
Present in the Senate after the Assassination of Ceasar, Mark Antony warned Aya that Brutus seriously miscalculated the consequences of Caesar's death. The people of Rome would not see Brutus as a liberator who killed a tyrant but as the murderer of their beloved general.
After the assassination of Caesar, Antonius, alongside Octavian, led a military campaign to take down the Liberatores, the forty Hidden Ones Senators who played a part in the assassination of Julius Caesar. A civil war followed, with the armies of Marcus Junius Brutus and Gaius Cassius Longinus facing those of Antonius and Octavian. In 42 BCE, the two sides clashed at the Battle of Philippi in Macedonia. Ultimately, Brutus and Cassius both took their lives in the face of defeat and the Roman Republic stood victorious.
Out of respect for Brutus, Antonius sent his most expensive purple mantle to Brutus' comrades for his body to be wrapped in it. The Assassins initially tried wrapping the body in the Shroud of Eden in an attempt to revive him, but were only momentarily successful. The Assassins stopped their attempt, and Brutus' corpse was then wrapped in Antonius' mantle.
In 38 BCE the Aya, now known as Amunet, informed her fellow Hidden One Bayek that Marcus, alongside his new lover Cleopatra, were becoming a problem. She noted that he had "the same stench of tyranny that Caesar did". 
- Assassin's Creed: Project Legacy (mentioned only)
- Assassin's Creed: Origins - The Hidden Ones (mentioned only)
- Assassin's Creed: Origins (comic) (first appearance)