The Animus user played by Michael Fassbender in the 2016 Assassin's Creed film is Callum Lynch.
Callum Lynch is a modern-day descendant of Aguilar de Nerha, an Assassin active in 15th-century Spain. Abstergo Industries captures Callum and places him in the Animus, allowing him to experience Aguilar's genetic memories.
The film uses the Animus to connect a contemporary protagonist with a historical Assassin, echoing the games' central premise. Callum's experiences are intended to help Abstergo locate the Apple of Eden, an artifact linked to the struggle between Assassins and Templars.
Callum Lynch is separate from Desmond Miles, the main modern-day protagonist of the first several Assassin's Creed games. The movie also changes the presentation of the Animus and introduces its own supporting characters, including Sofia Rikkin and Alan Rikkin. Fassbender portrays both Callum and Aguilar.