In Assassin's Creed: Revelations, Desmond Miles narrates the modern-day sections through the Animus.
Revelations follows Desmond after the events of Assassin's Creed: Brotherhood, when his mind is trapped inside the Animus. The game's modern-day sequences take place in the Animus Island and explore his memories, identity, and connection to the ancestral lives being accessed.
The historical campaign is experienced through Ezio Auditore's memories, with sections involving Altaïr Ibn-La'Ahad. Desmond therefore serves as the modern-day protagonist and framing character, while Ezio and Altaïr occupy the historical layers.
Clay Kaczmarek is another modern-day Assassin linked to Animus memories, but he is not the narrator of Revelations. William Miles is Desmond's father, and Rebecca Crane supports the team as a technician.