The machine that lets modern characters relive ancestral memories in Assassin's Creed is the Animus.
In the series, the Animus is a device that accesses genetic memories inherited through a person's ancestry. A modern user enters the machine and experiences a reconstructed historical life, allowing the games to move between contemporary storylines and past settings.
Desmond Miles uses an Animus in the first games to experience memories belonging to ancestors such as Altaïr and Ezio. Abstergo Industries, the corporate organization associated with the Templars, develops and operates several Animus systems.
The Animus is fictional, and the series treats genetic memory as a science-fiction premise rather than an established biological phenomenon. It is distinct from the Apple of Eden, a powerful Isu artifact, and from the Helix, a later entertainment-oriented Animus interface.