Desmond Miles is the Animus user who experiences Ezio's memories in Assassin's Creed II.
Desmond is a modern-day descendant of several important Assassin figures. In the present-day sections, he uses the Animus, a machine that reads genetic memories, to relive the experiences of his ancestor Ezio Auditore during the Italian Renaissance.
The modern storyline is central to the first five major games. Desmond begins as a former Assassin who has been captured by Abstergo Industries, the modern corporation connected to the Templar Order. His time inside the Animus helps the Assassins locate artifacts and understand threats in the present.
William Miles is Desmond's father, not the Animus subject in Assassin's Creed II. Warren Vidic is an Abstergo scientist, while Shaun Hastings is an Assassin analyst who joins the modern team later in the series.