Black Heart

The Black Heart was an entity of Darkness worshiped by the Vex, with the ability to unify all Vex minds as one. It was located deep within the Black Garden and is heavily defended by the Sol Divisive, a religious programming of Vex who worship the Black Heart as a god. It serves as the main antagonist of Destiny.

History
Near the Black Heart are three massive Vex who collectively make up a programming called the Sol Progeny: The Eschaton Mind, who represents the future and end of the world; the Imminent Mind, who represents the present at any moment; and the Primeval Mind, who represents the past and the beginning of time. These three defenders appear in some type of stasis until struck by the powers of the Black Heart, allowing them to reincarnate as normal Vex and fight off any intruders. The destruction of all three Sol Progenies will result in the destruction of the Black Heart. Destroying the Black Heart enables Light to begin returning to The Traveler.

The Undying Mind, a Vex Hydra, attempted to revive the Black Heart and re-establish Vex control over the Black Garden, but was stopped by the Guardian and their fireteam.

It was theorized by Uldren Sov that the Black Heart acted as a "tripwire" for an unknown force to recognize when Light was returning to the Traveler.