Astronomican - History: At the very start of the Great Crusade in ca. 798.M30, the planets closest to Terra were easily reached by blind jumps through the Immaterium. The Empyrean of that time had only recently calmed after the great turbulence of the Age of Strife following the birth of the Chaos God Slaanesh.However, it soon became clear that to travel further from Terra, the Imperium's Navigators would require a stable astronavigational reference point within the Immaterium to triangulate their current location against if longer Warp jumps were to be attempted with any hope of success.Following the successful conclusion of the Unification Wars, the Emperor first ordered the construction of the Astronomican on Terra, which would enable His forces to expand the Great Crusade to the stars beyond Sol. Huge numbers of Tech-priests were brought from Mars to oversee the project and the majority of the Terran population was drafted to construct the towering machine-buildings needed to support this labour.At the time the Astronomican was the single largest artifice on Terra, and the entire device was merely a focus through which the Emperor could direct His fathomless psychic energies to generate a partly self-sustaining telepathic signal through the Empyrean (although few were aware of this fact).The psychic navigational beam the Astronomican generated was able to propagate through the Warp and those attuned to its unique frequencies and modulations, the Navigators, were able to use it as a beacon and pole star when plotting journeys through the Immaterium. By this beacon the Warp could be travelled at speeds and with a margin of safety that had been unprecedented, although the risk could, of course, never be fully mitigated.The Astronomican was an incalculable boon to both the Great Crusade and the fledgling interstellar domain of Mankind that it was creating. In a similar way, the Emperor was able to shut down the Astronomican or interrupt the beam at will.Only a handful of individuals knew that the great signal was actually powered by the Emperor's psychic powers, and they lived in fear that should He be disabled or killed, the galaxy would be plunged into a new Age of Strife. Such was the Astronomican's effect that even in that distant age of the Imperium's first founding some referred to it as the "Divine Light," or the "Emperor's Light," often without fully realising the literal truth of those words.With His Imperial Webway Project only in its planning stages, the Emperor resorted to powering such a reference point Himself, using the focus chamber He had built earlier beneath the Imperial Palace to project a beam of unimaginable psychic power and range through the Warp. So colossal was the Emperor's psychic might that in the early days of the Great Crusade in the late 30th Millennium He could power the Astronomican while He was off-world, leading the Imperial war effort personally at the head of the Principia Imperialis expeditionary fleet.For all His might, however, the Emperor still had limitations, and the task of powering the Astronomican so that its beacon was perceptible over the whole of the territory of the growing Imperium of Man became more and more taxing, weakening Him to the point He was nearly choked to death by a powerful Ork Warlord on the world of Gorro, only to be saved in the nick of time by His Primarch son Horus.The ever-growing demand of projecting the Astronomican upon the Emperor was one of the reasons He handed command of the Great Crusade over to the Warmaster Horus after the victorious Ullanor Crusade against the Orks and returned to Terra to complete His Webway Project, an initiative intended to make the Astronomican all but unnecessary.With an Imperial extension into the Aeldari Webway, the starships of Mankind would be able to cross the galaxy in the blink of an eye without having to deal with the deadly dangers of the Warp. Alas, such a dream was not to be, and the Webway Project was destroyed by the machinations of Chaos during the Horus Heresy.