Eye of Harmony

In the fictional world of Doctor Who, the Eye of Harmony is the nucleus of an artificial black hole created by the Time Lords to provide energy for their home world of Gallifrey and their time travel technology.

The Eye was originally mentioned in the Fourth Doctor serial The Deadly Assassin (1976), where it was revealed as the source of power that sustained Gallifrey. According to the ancient records, the legendary Time Lord Rassilon captured and placed the Eye - the nucleus of a black hole - beneath the Time Lord's citadel on Gallifrey (the Panopticon). Rassilon placed the black hole's nucleus in an eternally dynamic equation against the mass of Gallifrey and so that as long as the Eye existed in this "balanced state", the power of the Time Lords would "neither flux nor wither". However, it remained there so long that it passed into legend. Until the Fourth Doctor and the renegade Time Lord known as the Master rediscovered it in The Deadly Assassin, the Time Lords had forgotten its location, some even believing it to be mythical or no longer in existence.

As seen in The Deadly Assassin, the Eye was linked to two other Gallifreyan artifacts, the Sash of Rassilon and the Great Key of Rassilon. The Sash was essential for the wearer to control and manipulate the Eye safely without being sucked into its gravity well and the Great Key was an ebonite rod that could be used to drain energy from the Eye. The Great Key was later renamed the Rod of Rassilon in The Invasion of Time (1978) to distinguish it from the other Great Key, a component of the De-mat gun.

In The Deadly Assassin and the 1996 Doctor Who television movie, the Master tried to use the Eye to steal himself a new set of regenerations from the Doctor.

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