In a vain attempt to satisfy the eternal hunger, a swarm of tyranids wanders through the cold expanses of space, destroying all life on oncoming planets. The forces of the Imperium face the most difficult test - the enemy is practically invulnerable and is able to easily adapt to the most hostile environment. The warriors of the Order of the Ultramarines stand up to defend the Imperium shoulder to shoulder with their brothers in blood and arms - the fighters of the Order of Mortifacts. In order to defeat the bloodthirsty aliens, the commander of the Fourth Company of the Ultramarines, Captain Uriel Ventris, has to take part in a dark barbaric ritual and deviate from the ancient principles set out in the ancient Codex Astartes...