The Golden Throne is an immense and arcane device housed within the deepest sanctum of the Imperial Palace on Holy Terra, upon which the Emperor of Mankind has been interred for ten thousand years. Part life-support machine, part psychic amplifier, and part relic of a lost age of human science, it sustains the ruined body of the master of mankind long past the point where ordinary death would have claimed him.
Following the treachery of the Horus Heresy, the Emperor was left broken and near-lifeless, and his shattered form was placed upon the Throne so that his will might endure. From this seat his mind projects across the void, most crucially powering the Astronomican, the psychic beacon by which the ships of the Imperium navigate the tides of the warp.
The device demands a terrible price. Its ancient mechanisms decay faster than they can be repaired, and its operation is said to consume the souls of thousands of psykers daily. Few living beings understand its inner workings, and the fear that it may one day fail hangs over the Imperium like a shroud. The Throne is thus both salvation and slow tragedy, a golden cage keeping humanity's god perpetually between life and death.