The thirty-second millennium is underway, and the Heresy Wars have become a vague memory. After centuries of peaceful life, the Imperium is in panic: orcs are attacking human possessions everywhere. The alien assault moons, like an unstoppable wave of destruction, destroy planet after planet with gravitational weapons of irresistible power. The High Lords of Terra, paralyzed by the horror of such a massive threat, find themselves unable to act effectively. With entire Space Marine chapters dying or missing in action, will anyone have the will and strength to stand up for the Imperium?