The Animus is the fictional device that accesses ancestral memories in Assassin's Creed. It allows a modern user to experience genetic memories inherited from an ancestor, turning historical events into playable sequences.
In the first game, Desmond Miles is forced to use an Animus by Abstergo Industries. The company claims that the device is being used for research, but Desmond gradually discovers that Abstergo is the modern face of the Templar Order. His sessions center on the memories of Altaïr Ibn-La'Ahad.
The Animus explains how the series can move between modern-day scenes and different historical periods without treating the player as literally traveling through time. It also supports the franchise's recurring ideas about memory, genetic inheritance, surveillance, and control.
Later games show revised Animus models, portable systems, and the Helix entertainment platform. Helix is related to Abstergo's technology, but it is not the name of the original memory-access device.