Desmond Miles uses the Animus to relive genetic memories in the original Assassin's Creed game.
In the modern-day storyline, Abstergo Industries captures Desmond and places him in the Animus, a machine that reconstructs ancestral memories from genetic data. The process allows him to experience the life of Altaïr Ibn-La'Ahad during the Third Crusade.
Desmond is not the historical assassin he controls. He is a modern descendant of several important Assassin figures, and his ancestry becomes a major narrative device across the early games. The Animus sequences therefore connect a contemporary science-fiction plot with historical action gameplay.
Players sometimes confuse Desmond with William Miles, his father, or Clay Kaczmarek, another Animus subject. Desmond remains the central modern protagonist of the first several mainline entries, although later games reduce or change the player's modern-day role.