Desmond Miles is the Animus user who appears in the first five main Assassin's Creed games. Through the Animus, he relives the genetic memories of ancestors including Altaïr Ibn-La'Ahad, Ezio Auditore, and Ratonhnhaké:ton.
Desmond's modern-day storyline connects the historical campaigns. After being taken by Abstergo Industries, he is placed in the Animus and forced to access ancestral memories. He later works with the Assassin team led by his father, William Miles, using the machine to uncover information needed in the conflict between Assassins and Templars.
The five games are Assassin's Creed, Assassin's Creed II, Brotherhood, Revelations, and Assassin's Creed III. Layla Hassan becomes the principal modern-day viewpoint in Origins and later games. Rebecca Crane is a member of Desmond's support team, while William Miles is his father, so neither is the Animus subject asked for here.