It is one of the most iconic objects of the 40k universe, it is associated with the Emperor to the extent that the two are both literally and figuratively inseparable, but we know next to nothing about it.
It seems to be a fundamentally given piece of knowledge that the Golden Throne exists and has always existed but we never seem to question where it actually came from. What little we do know tells us that its current role as an advanced life-support system is not what it was originally designed for; this capability was a modification of the device done to the specifications of the mortally wounded Emperor himself. Originally the Golden Throne was a key component of the Emperor’s top secret project, a project that he considered so important that he effectively withdrew from the Great Crusade even as it seemed to be nearing its triumphant conclusion, becoming all but a recluse in the bowels of the Imperial Palace while leaving the crusade and running of his Empire to his sons and the Sigillite.
In truth this project was an ambitious effort on his part to open an Imperial route into the Webway.
At first glance this project seems like a poor reason for him to withdraw from the Crusade, it seems like the benefit was of limited utility for him to justify withdrawing from his empire at such a crucial stage of transition. Clearly it would make interstellar travel easier, faster, and safer (radically so) which presents some huge advantages to a galaxy spanning power, but if you consider it the Eldar could and still can do this, and it hasn’t made them (or their old empire) untouchable or all-powerful. However, when one takes a second to reconsider what he was working on was subtly but SIGNIFICANTLY more important than merely gaining access to the Webway. The Emperor is testing the ability to alter and expand it, he didn’t simply kick in the door and gain access to a preexisting network, he created a new link in that network of his very own. This is something that (as far as we know) NO ONE since the Old Ones who originally created the Webway had the ability to do. If he could do it once on a small scale, then in time he could work out how to do it again and on a much larger sale, reshaping the Webway however he needed it, creating new paths of any desired size between any desired locations, enabling humanity to travel from practically any point in the galaxy (or perhaps the entire universe) to virtually any other.
An interesting fact about the Golden Throne is revealed through Magnus’s disastrous effort to psychically warn the Emperor of Horus’s treachery. Magnus understood in the moment of his contact with the Emperor that his very intrusion had caused perhaps irreparable damage to unfathomably ancient components unearthed in archeological searches. These components were evidently psychically resonant, responding to and powered by psychic energies, originally powered by the Emperor himself. Magnus’ intrusion tore a hole from the Warp into the Webway and thence into the carefully warded research environment where the Emperor was working, in the process burning out many of the Golden Throne’s delicate components and leaving an open portal into the Webway and the Warp beyond. Similar technologies to those apparent in the Golden Throne were evident in the Akashic Field interface being developed by the Mechanicus on Mars just before the Heresy. Powered and controlled by the mind of a psyker the device bore both superficial and functional similarities to the Golden Throne of terra; both took the form of a “throne” or “chair” that both psychically shielded and physically supported the body of the psyker operating it and used a vast stable of other human psykers to create an array to augment, power, and focus its capabilities. Taken in concert with these facts it seems likely that the Golden Throne represents a fusion of human technology and elements of uncovered Old One technology to recreate the lost ability to modify and shape the Webway, the fact that it has been reduced to a glorified combination iron-lung, gatehouse, and lighthouse is a tragedy of epic proportions. The reduction from a device of grand ambition, innovation, and hope into a mechanism to merely preserve the status quo is a microcosm of the Imperium as a whole.
The Horus Heresy novels
Warhammer 40,000 Core Rulebook
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