Warhammer 40K: 10 Worst Things The Imperium Has Ever Done
9. Almost Purged All Life On The Moon
Empires do not simply arise from nowhere, they are forged over millennia of strife and conflict. This was no different for the Imperium of Man, which took ten thousand years to rise from the ashes of nuclear warfare which destroyed the Earth we know today.
One man known as the God-Emperor unified the Mad Max-like barbarian tribes into the beginnings of a unified Earth and began a crusade to conquer the galaxy. But conquering a galaxy requires complete control of humanity's solar system.
For Mars, their integration into the Imperium was quite smooth and extremely necessary for humanity to achieve space-age technology, the same could not be said of our own moon.
On the moon, there was a cult of gene manipulators who survived by creating new bodies for them to inhabit over and over again in order to achieve what they viewed as "the true personification of a single human archetype." This essentially meant the moon was haunted by immortal cultists that knew more about the human genome than anyone else in the galaxy.
Their gene technology was just as important to the great crusade as Mars' technology was, but the cultists on the moon refused to be controlled by Earth's people, and a quick war broke out leading to the first conquest of the Imperium of Man and the cultist's near extinction.