Emperor of Mankind

The Emperor of Mankind is the leader of the human Imperium, and is described by the Imperial Ecclesiarchy as the Father, Guardian and God of Humanity. He has sat immobile within the Golden Throne of Earth for ten thousand years. Although once a living man, his shattered body can no longer support life, and remains intact by a spirit itself sustained by the soul-sacrifice of countless millions. He has sacrificed his immortal life in the service of Man.

To Mankind's countless trillions across the galaxy-spanning Imperium, he is nothing less than a god. Through his Imperium, Mankind is held together and forms one of the strongest races in the galaxy, and united, Mankind is able to survive the myriad of threats it faces. His rule has been long and necessarily harsh.

The Emperor is at the very center of the Imperium. Although he is no longer directly involved in the day to day running of the Imperium, his presence on the Golden Throne is vital to sustaining the Imperium, as he sustains the Astronomicon, which allows for long-range warp travel, which is vital to Imperial shipping and communication. He is said to guide his race through the Emperor's Tarot, soul-binds psykers. He is said to constantly battle Chaos and prevent its intrusion upon the material universe. He must be constantly vigilant throughout the entire Imperium.

Origins
In the current background, the Emperor's origin and history prior to unifying Terra is left mysterious and undetailed. The first mention of the Emperor in Imperial records is when he unified Terra at the end of the Age of Strife. It is known he had been immortal and ancient even before his ascension to the Golden Throne ten thousand years ago, though the details of his origins and life prior to this are unknown to all but a few. He was born in the eighth millennium BC in central Anatolia, a place of barren mountains and cold streams.

The Emperor is the New Man, the first and greatest of the race of psykers. He is also the reincarnation of the extinct Shamans who had guided humanity. As he grew older his powers began to manifest themselves and he gradually remembered his thousands of past lives.

For thousands of years before becoming the Emperor, he guided and watched humanity develop. He was aware that the extreme sides of the human nature were feeding the Chaos gods, and sought to promote peace and harmony, and thus curb the growth of the Chaos Powers. The Chaos Powers themselves recognized the Emperor as their greatest enemy. Only during the Age of Strife did the Emperor emerge to take a more direct hand in the future of humanity, conquering the warring factions and establishing his rule over Earth.

With the assistance of the Adeptus Mechanicus on Mars the Emperor created the first Space Marines and the fleets of interstellar ships that would carry his armies across galactic space, to begin the Great Crusade that would unify mankind into one Imperium. The Emperor also created the Primarchs from whom the Space Marines' gene-seed was developed. The Chaos gods, however, sought to thwart his plan. The Primarchs were sucked into the warp, and scattered across the galaxy. During the Great Crusade all of the Primarchs were found and united with their Space Marine Legions. However the Emperor's most trusted Primarch, the Primarch Horus fell to Chaos and betrayed the Emperor, and along with "fully half" the Space Marine Legions, started a massive civil war for control of humanity. This rebellion is known as the Horus Heresy. Though the Emperor defeated Horus, he was all but destroyed in the battle; only the life-supporting Golden Throne has sustained his living corpse.

The Golden Throne is a massive and complex life support device encompassing the Sanctum Imperialis, the "throne room" of Emperor's Inner Palace. There the Emperor's physical form is preserved by the vast machinery of the Golden Throne, which itself is maintained by tech-priests of the Adeptus Mechanicus. The Emperor can only be sustained by the life energy of other psykers, which are brought to Terra aboard the infamous Black Ships. Connected to the Throne device, they are drained agonizingly of their psychic life energies, which is food to the Emperor. Only through this constant sacrifice can the Emperor, the Imperium and humanity survive.

The Star Child
The Star Child background was introduced first in the Realm of Chaos books and mentioned later in the 3rd Edition Warhammer 40,000 guide. The concept is similar to the Eldar potential god Ynnead forming in the Infinity Circuit.

The background has two aspects: the first is that the Emperor's soul is currently forming as a new entity (the Star Child) in the warp and that he will be reborn, and the second is that the Emperor had children. (Realm of Chaos: The Lost and the Damned)

Over the almost 40,000 years the Emperor walked among mankind he formed many families and fathered children. A few of his descendants have inherited the powers of the Star Child. These are the Sensei. A hidden group that call themselves the Illuminati know the Emperor is failing. They also know of the Fall of the Eldar and seek to prevent Man's own fall to Chaos. The Fall of Man to Chaos would create a new Chaos god, and with its birth, a new warp/real space overlap, encompassing the entire Imperium. They gather the Sensei together, protect them from the Inquisition, and pave the way for the rebirth of the Emperor. Their plan is ultimately to sacrifice the Sensei to the Emperor at the moment the Emperor finally fails; he will be renewed, and be reborn as the Sensei-Emperor to again lead his race in person.

While the Star Child background was introduced in the original 40K version, and dismissed as heretical in 3rd edition in favor of the more vague "Iron Men and Stone Men" history, the current Inquisition's Thorians believe in a similar concept of the Emperor's rebirth.

The Emperor is the incarnation of the extinct Shamans who, with their prophetic powers and connection to the warp in its natural and uncorrupted form, had guided ancient mankind. After Horus rebelled and destroyed the Emperor's mortal frame, his body and soul could no longer remain as one; his soul melted into the warp, only a tiny core of the Emperor's humanity remaining whole, which was like a small child in a tiny reed boat adrift in the storm of the warp. Since the Emperor's soul survived, there was a possibility that his whole essence could be reborn once more.

In the same way the Shamans died together to reincarnate as the Emperor, the Emperor's death too could herald a new savior. That time would lie far in the future, when mankind's desire for a new savior would strengthen the core of the Emperor's soul and rekindle it to new life.

The soul of the Emperor adrift in the warp is the Star Child. The humans that were left in charge of the Imperium had no real understanding of what had happened to the Emperor. Though the Emperor's body continued to live within the Golden Throne and his mind continued to be a beacon for humanity, his soul is a god waiting to be born.

The Star Child is also suggested as being the compassion which the Emperor thrust from himself in order to destroy his most beloved Primarch-son, Horus. (Inquisition War Trilogy novel series, Ian Watson, Black Library Publishing)

The Inquisition (particularly the Ordo Malleus) has always been at war with the Sensei, the "Emperor's Sons." In 997.M41, Inquisitor Fortez reports that he and his colleagues Alexio and Credo determined the Temple of the Star Child on Levilnor IV consisted of unwitting pawns of Tzeentch, so they eliminated it (Warhammer 40,000 3rd Edition Rulebook, p. 272). While it has never been confirmed, it has been hinted that ammunition for the Inquisition's Psycannons and Psyk-Out bolter rounds are partially composed of rendered down Sensei.