Anacletos was an orphan sold into slavery at a young age to become a gladiator. As he fought in the arenas to survive, his emerging skills were recognized by the Templars, who soon recruited him to their cause. From there on, he hunted his targets with dedication and ferocity. Despite being a Templar, Anacletos was not concerned with the ideals of the Order, instead using his allegiance to justify killing.
In 2012, his genetic memories were used as an Animi Avatar by the Templar company Abstergo Industries, in the second stage of training for their Animus recruits, under the title of the Gladiator.