Which modern-day character uses the Animus in the original Assassin's Creed?

Desmond Miles uses the Animus in the original Assassin's Creed.

Desmond is a modern-day descendant of several important Assassin figures, including Altaïr Ibn-La'Ahad. Abstergo Industries, a modern corporation aligned with the Templars, captures him and places him in an Animus so researchers can access his genetic memories. Through the device, Desmond relives Altaïr's experiences during the Third Crusade.

The Animus is a fictional machine that allows a person to experience ancestral memories encoded in DNA. This device explains how the game moves between a contemporary storyline and historical settings without treating the historical scenes as ordinary time travel.

Desmond is sometimes confused with William Miles, his father and a senior Assassin, or with Layla Hassan, who becomes the modern protagonist in later games such as Origins. Rebecca Crane is also involved with Animus technology, but she is not the user in the original game's central framing story. Desmond's role continues across the early main entries.