Which Assassin's Creed game first introduced the Animus concept to players?

The first Assassin's Creed game introduced the Animus concept to players.

The Animus is a fictional machine that allows a person to access genetic memories inherited from ancestors. In the original game, modern-day bartender Desmond Miles is forced to use the machine by Abstergo Industries, whose modern organization is linked to the Templars.

Through the Animus, Desmond experiences the life of Altaïr Ibn-La'Ahad during the Third Crusade. This framework explains why the series can move between historical periods while retaining a modern storyline and recurring conflict.

The Animus is often described as a time machine, but it does not send characters physically through time. It is a device for experiencing ancestral memories. Later games expand the technology and introduce new users, but the concept originated with the 2007 original.