Desmond Miles is the Animus user who experiences ancestral memories in the first Assassin's Creed game.
Desmond is a modern-day descendant of the Assassin Altaïr Ibn-La'Ahad. Abducted by Abstergo Industries, he is placed in the Animus, a machine that reconstructs genetic memories. By reliving Altaïr's experiences, Desmond helps Abstergo search for information connected to the Assassins and ancient artifacts.
The Animus framework lets the series move between a modern storyline and historical settings without treating the historical sections as ordinary time travel. Desmond's role continues through several early games, including Assassin's Creed II, Brotherhood, Revelations, and Assassin's Creed III.
William Miles is Desmond's father, while Warren Vidic is an Abstergo scientist involved in the Animus project. Clay Kaczmarek is another modern-day character linked to the Animus, but he is not the user in the first game's central storyline.