The world of Idos is on the verge of destruction, wracked by catastrophic storms and plagued by ravening tyranids. Into this maelstrom come the Raven Guard 4th Company, the warzone perfectly suited to their lightning-strike methods of combat. Led by Veteran Sergeant Grayvus, their mission is simple – to rescue the planet’s last survivors. But in the midst of this nightmare, they receive new orders to locate and destroy a power station. The station is built upon a fault line, and the resulting quake would swallow thousands of tyranids and turn the war in the Imperium's favour. Grayvus and his company must fight their way through genestealers, acid spore mines and a deadly biomorph if they are to succeed and reclaim Idos for the Imperium.