The Animus is the device that allows a user to relive an ancestor's memories in Assassin's Creed.
In the modern-day storyline, the Animus reads genetic memories stored in a person's DNA and reconstructs them as an interactive experience. Desmond Miles uses the machine to access the lives of ancestors such as Altaïr Ibn-La'Ahad and Ezio Auditore, while later games introduce other users and Animus-related systems.
The concept gives the series a structure that alternates between historical settings and a modern narrative. It also explains why a player can control a historical character without that character being physically present in the modern world.
The Animus is often confused with Eagle Vision, which is an Assassin ability used to perceive people and objects in unusual detail. The Apple of Eden is a powerful Isu artifact, not a memory-reading machine. The Bleeding Effect is a side effect of repeated Animus exposure.