The Emperor: The Emperor is the center of the Imperial Cult, incarcerated in his Golden Throne for over ten thousand years. He is unable to move or speak, and has been so since the Horus Heresy when he barely defeated Warmaster Horus in single combat. Since then he has been revered through pious doctrine of the Ecclesiarchy, with only their version of his life story known to the citizens of the Imperium.
He was born in the eigth millenium BC in modern day Turkey (Central Anatolia), when humans were in touch with a peaceful and natural Warp. His birth was the conclusion of a centuries long debate by the most powerful Shamans on earth, when they all became reincarnated inside one body.
With all of this power incarnated in one man, the man who was to become the Emperor of mankind had many gifts. He could easy suffering, read minds and most importantly, live forever. At first he didn't use these gifts, but as the millenia passed he began to help with his knowledge and powers, always disguising himself as a normal person. Through out his actions he took many guises, but always knew the path upon which he must direct humanity.
Staying on Earth would have doomed Humanity to the thread of Chaos. Instead the Emperor directed humanities advances into space technology through the second, third and fourth millenia, allowing them to colonise the galaxy. Later, he cast off his many guises to take control of Earth and its empire as The Emperor, awaiting a chance to reconquer the galaxy.
In his plans to combat the Chaos Powers, The Emperor created the Primarchs. He hoped to create an entire race of super-humans immune to Chaos, but his plans never came to full fruition.
When the warp storms that followed the scattering of the Primarch's subsided, the Emperor began The Great Crusade. He began tracking down the scattered Primarchs, returning them to his side and removing the taint of Chaos from each human planet.
After many millenia with the Primarch's back by his side, the Emperor suffered the greatest betrayal when Warmaster Horus and nearly half of the Space Marine legions turned traitor and sided with Chaos. After what is another chapter in the history of Humanity, The Emperor defeated Horus, although not without great loss to himself. Since that fateful battle where he was almost slain, he has been encased in his Golden Throne where he has remained alive but silent for the past ten thousand years.
The Emperor's soul now drifts at one with the Warp, as the souls of the ancient Shamen did. The protection and support of the Golden Throne held his body just before death, allowing him an anchor in the Imperium and a possible means of communication. Although his body is broken and his soul is awaiting reincarnation, the leaders of the Imperium believe him to be alive, not even considering the fact that he may be reborn. Only a select few, the Illuminati, know of the rebirth of the Emperor, and they are often perceived as heretics and so must manipulate the path of humanity from the shadows as the Emperor once did.
When he will return is unknown, but the power of the Emperor in his Golden Throne and the power of the Ecclesiarchal doctrine is enough to keep the Imperium together and strong. Thorian Inquisitors believe that the Emperor will, one day, be reincarnated.
During Inquisitor Draco's expedition in to the Emperor's Throne Room it emerged that his mind is split in to several persona so that he can watch over the Imperium, soul-bind psykers, watch the Warp and beam the Astronomican, as well as receiving information and granting audiences.
Source: Draco by Ian Watson, Realms of Chaos: The Lost and the Damned by
Submitter: IBBoard