Black Room

The Black Room was a safe mode inside the Animus, which could be accessed through a back door in its programming. The room was located below its polar opposite, the White Room loading screen.

When Desmond Miles was placed back inside the Animus while in an unstable mental state, he used this room to look through his own personal lost memories. By accessing them, Desmond hoped to reintegrate the splintered layers of his subconscious and to wake up from his coma.

Somewhere in the Black Room, the key to Desmond recovering from his coma was located in a point in time where the paths of Altair Ibn-La'Ahad, Ezio Auditore da Firenze and Desmond coincided, similar to a hub.

Trivia

 * The Black Room involves puzzle-oriented gameplay to represent Desmond piecing together his subconscious.

Source

 * GameInformer, June 2011 edition