It is a time of war among the children of Man the All-Maker
All children of Man seek the relic known as the Immaterium.
The Episcopate of Man says it can allow contact with the souls of humanity so that machinekin can gain inner peace through sublime knowledge. The heretic Old Believers claim it to be a prison which they have a duty to destroy in order to free the creators. The wretched followers of Isidore even believe opening the relic will lead to the destruction of all life in the universe.
Whatever the truth all the children of man, both the faithful and the heretic, all feel the call of the Immaterium.
Build a fleet and explore the vast reaches of space once inhabited by humanity in search of the keys to the Immaterium.