The Animus is the fictional device that lets Desmond Miles relive ancestral memories. In Assassin's Creed, it reads genetic memories encoded in a person's DNA and presents them as interactive experiences.
Desmond uses the Animus to access the lives of ancestors such as Altaïr Ibn-La'Ahad and Ezio Auditore. This framing device allows the series to move between a modern-day storyline and historical periods without treating time travel as the mechanism.
The Animus is developed and controlled by Abstergo Industries, the modern organization linked to the Templars. Later games introduce newer versions, including portable or simulated systems, but the basic purpose remains the exploration of genetic memories.
The Animus is often confused with the Apple of Eden, which is an ancient Isu artifact. The Bleeding Effect is also different: it is a side effect in which skills or memories from an ancestor influence the person using the Animus.