Desmond Miles is the main modern-day protagonist throughout most of the original Assassin’s Creed games.
Desmond is introduced as a former Assassin who is abducted by Abstergo Industries. The company places him in the Animus so it can examine the genetic memories of his ancestors, beginning with Altaïr Ibn-LaʼAhad in the first game.
Across the early series, Desmond relives memories connected to several ancestors, including Ezio Auditore and Ratonhnhaké:ton. His modern-day storyline gradually becomes as important as the historical adventures because he learns about the conflict between the Assassins and Templars.
The wording “most of the original games” matters because later titles shift their modern-day focus. Assassin’s Creed Origins introduces Layla Hassan, while Desmond’s major story concludes in Assassin’s Creed III. William Miles is Desmond’s father, not the protagonist of those Animus sequences.