The virtual-reality device used to explore ancestral memories in Assassin's Creed is the Animus.
Within the series, the Animus allows a user to access genetic memories inherited from ancestors. The machine converts those memories into an interactive simulation, letting modern characters experience historical events from an ancestor's perspective. This technology connects the contemporary storyline with the series' historical adventures.
Desmond Miles is the first major modern-day user shown in the original game. Later stories introduce other users, operators, and Animus-related systems. The device also provides an explanation for gameplay features such as revisiting memories, synchronizing actions, and displaying information about historical environments.
Helix is a later entertainment and memory-experience system associated with Abstergo, not the general name for the original device. Eagle Vision is an Assassin ability used to identify people and objects, while an Apple of Eden is a powerful Isu artifact rather than a memory machine.