‘It may prove to be vital,’ the Lion said.

The gold-plated double doors of the Exaltatio Angeli librarium had been ripped from their hinges, and their engravings bubbled, the shapes of heroic war transformed into a nightmare tangle of insectile limbs. Plague daemons stumbled down the aisles, their rotten swords hacking at books, turning them into liquefying pulp. In the centre of the great hall, there were other abominations. They were vortices of flesh and flame, headless cones of screaming mouths that breathed the fire of nightmare against the towering shelves. They whirled from lectern to lectern, and rampaged through the marble bookcases. Vellum or data-slate, metal or stone, whatever they touched burned and changed.

The Exaltatio Angeli had been badly damaged in the Red Tear’s fall to Signus Prime. Hundreds, perhaps thousands, of irreplaceable tomes had been lost, swaths of the history of the Blood Angels and the culture of Baal swept into oblivion. Sanguinius regarded what had been salvaged as even more precious. These books were more than records now. They were survivors in their own right, every scar and burned page a mark of the new chronicle, and of the cost it exacted. Now they were dying, and worse. The corpulent monsters, their bodies leaking decay, were killing the memory of Baal, turning it into a rotten swamp. Fungus and mould sprouted on the spines of books at their passage. Tentacles and grasping fingers grew from the volumes. Data-slates spread wings and flew about the wide central space of the librarium. Scrolls became tongues. They slipped off the shelves like long white slugs, babbling words that belonged to no tongue in the material galaxy. As they chanted, the air flaked into ash around them.

A squad of Blood Angels led by Sergeant Orexis fought the incursion in the librarium. Two five-man teams had taken up positions on opposite sides of the bronze-railed gallery that ran around the centre. They had a wide field of fire and were pumping bolter shells into daemons on all six levels. Each shot was sniper-precise. They fired in short bursts, keeping firm control over the spread of their projectiles. They were trying to preserve the Exaltatio Angeli as much as purge it of the daemonic presence.

The Angel swept his gaze over the first level of the Exaltatio and had to transmute despair into anger. The mutations were worse than the destructions. What had rotted was dying, already gone. What was changed was more insidious.