Emperor of Mankind
The origins, and original name, of the Emperor are not known. Some have theorized that he was born approximately 8000 BCE (-8M) in central Anatolia. He grew up within an isolated and meagre territory, and it was rumoured that he has the power to stop his own aging and numerous other psychic abilities. After many years passing, the Emperor became more wise and focused. He intuitively knew of the corruption of Mankind's behavior and set out to correct it. Each time he intended to stay in the background. He was not always successful,and without intent, he became a leader. Over the years he collected even more advanced wisdom and is known as the facilitator of most of the important inventions of mankind.
The first mention of him in Imperial records is when he conquered Terra after the Age of Strife (sometime in the 29th Millennium). The Emperor's use of genetically engineered warriors enabled him to reunite the people of Earth, and to set his sight on the stars. With the assistance of the Adeptus Mechanicus on Mars the Emperor created the first Space Marines and fleets of interstellar ships to carry his glorious armies to the farthest reaches of the Galaxy. The Emperor also created the Primarchs from whom the Space Marines' gene-seed was developed, however the Chaos gods had scattered them across the Galaxy. During the Great Crusade all of the Primarchs were found and reunited with their Legion of Space Marines. However the Emperor's most trusted servant Horus turned on the Emperor and along with nearly half the Space Marine Legions started a massive civil war. This period of turmoil became known as the Horus Heresy. Though the Emperor defeated Horus, he was badly wounded in the battle, after which he "ascended" the Golden Throne, where he remains to this day, neither living nor dead.
The Golden Throne is a complex life support device located in a massive complex over what was the British Isles, with the throne itself being over where Nottingham is in the real world. There the Emperor's physical form is preserved and his life functions are carried out by carefully-maintained machinery. The Golden Throne is connected to a massive warp beacon known as the Astronomicon that generates the system of signals making faster than light Warp travel in the Imperium possible. To provide the psychic energies necessary to maintain the beacon, hundreds of carefully-selected psykers are brought into the Golden Throne complex every day, where their life energies are absorbed by the Emperor, leaving them lifeless husks in a matter of weeks. Those selected to replace the used-up psykers consider it a great honor.
