The Imperium has been brought to the edge of extinction by an ork invasion of unprecedented scale and depth. Piecemeal strikes against the invaders prove ineffective - for every ork fleet destroyed, five more appear.
The only solution is to find and kill the orks' warlord - the Great Beast. Surely if its leader is killed, the greenskins' empire will fall apart in agony of infighting and confusion. Lord Commander Koorland assembles a mighty army, but when they arrive on the orks home world, the forces of the Imperium discover they have disastrously underestimated the might and ingenuity of their enemy.