Cassius

"No, we're still marching. But when we get there, we're going to visit a few old friends starting with Brutus and Cassius."

- Julius Caesar on his future killers

Cassius was a Roman senator in the Ancient Rome, who conspired and eventually proceeded with the killing of emperor Julius Caesar during the event known as Ides of March.

Averted Timeline
In the averted timeline Julius Caesar knew that his friend, Cassius would eventually conspire to kill him due to owning a Rise of Rome book from the future he stole from Nate Heywood. After marching to Rome after winning the Gallic Wars with his legion, Caesar killed both Cassius and Brutus.

Current Timeline
When the timeline was restored, Cassius proceeded with killing as in the original timeline.

Powers and abilities

 * Political acumen: As a Roman senator Cassius has enough political influence to conspire and kill Julius Caesar.

Equipment

 * Dagger: Cassius owned a dagger with which he proceeded to personally stab Caesar.

Behind the scenes

 * In real world Gaius Cassius Longinus was indeed a Roman senator, a leading instigator of the plot to kill Julius Caesar. He was also a brother-in-law of Brutus, another conspirer and killer mentioned by Caesar in the series.