The Devastation of Baal was the harrowing siege of the Blood Angels' homeworld, one of the gravest trials ever to befall that noble Space Marine Chapter. It came when a vast splinter of a tyranid hive fleet, drawn by the psychic beacon of the sons of Sanguinius, descended upon the Baal system to consume it utterly.
Aware of the doom bearing down upon them, the Blood Angels summoned their successor Chapters home, gathering nearly every warrior of their bloodline to a single desperate defence. The battle that followed was one of unimaginable ferocity, as the defenders fought to hold their sacred worlds against a living tide that seemed without end. World by world the outer defences were devoured, and the Chapter was ground down toward annihilation, its heroes falling one after another.
At the very brink of extinction, salvation came from an unlikely quarter: the opening of the Great Rift tore across the heavens, and the warp storms and daemonic incursions that followed disrupted the hive mind's assault. Reinforcements arrived, and the surviving defenders endured, though their homeworld was left a ravaged husk. The Blood Angels had survived, but only barely, their bloodline gutted and their fortress-monastery standing amid ruin. For more, see the Devastation of Baal.