Desmond Miles is the Animus user who experiences historical memories in the first Assassin's Creed.
Desmond is abducted by Abstergo Industries and forced to use the Animus, a machine that allows a person to relive genetic memories inherited from ancestors. In the first game, he experiences the memories of Altaïr Ibn-La'Ahad, an Assassin living during the Third Crusade.
Although Desmond is not the historical character controlled during most missions, his modern-day perspective frames the adventure. He learns that Abstergo is connected to the Templars and that the Animus is being used to locate powerful Pieces of Eden.
Desmond remains the central modern-day protagonist through Assassin's Creed II, Brotherhood, Revelations, and Assassin's Creed III. William Miles, his father, is a different character, while Warren Vidic is an Abstergo scientist involved in the Animus project.