The Razing of Prospero is an omnibus in the Horus Heresy Series, collecting Graham McNeill and Dan Abnett's duology focusing on the Burning of Prospero, and related short stories.
Not all of the primarchs were created equal. Long persecuted for his Legion's sorcerous ways, Magnus the Red nevertheless considered himself among the most loyal of the Emperor's Sons. It was he who first learned of Horus's corruption, but in trying to warn his father he earned the wrath of Leman Russ - primarch of the Space Wolves and self-styled Imperial executioner. Word of the subsequent attack on Prospero blurred the lines between ally and enemy, friend and foe, throughout the Legions. Seeking only unity, the Imperium engineered its own downfall.