In Assassin's Creed Revelations, Desmond relives the memories of Altaïr and Ezio through the Animus.
Ezio Auditore is the main playable Assassin in the historical storyline, which takes place largely in Constantinople in the early sixteenth century. Ezio travels there to investigate Altaïr's legacy and the Masyaf keys, linking the plots of the first game and Assassin's Creed II trilogy.
The Animus allows modern characters to experience genetic memories inherited through an ancestral line. Desmond's sections take place in the present day, while special memory sequences let him revisit earlier moments in his own lineage and resolve the psychological damage caused by prolonged Animus exposure.
Revelations is designed as a narrative bridge. It concludes Ezio's story, provides additional chapters in Altaïr's life, and advances Desmond's modern-day arc. Connor and Edward belong to later entries, so they are not the two earlier protagonists revisited here.