Not two metres away another of the robed cultists went down as Brother Yergen, of Tactical Squad Vincien, continued his blooding, punching his gleaming silver left hand right through the chest of a Shinarii.

Gdolkin brought his axe across in a scything blow, the monomolecular edge of the disruption field-sheathed blade slicing through not one, or even two, but three sabre-wielding fanatics. Three more swift strokes turned them into just so many bundles of black cloth-wrapped body parts. Behind him Joab XIII and Ishmael 192 continued to hold back the masses with blasts from their shoulder-mounted heavy weapons.

There was a flash of white to his left and Gdolkin glimpsed Apothecary Caduceus, his armoured form vividly bright amidst the dark robes of the Shinarii, do away with one of the Chaos devotees by plunging the spike of his progenoid-extracting reductor through the screaming maniac's eye so that it punched out the back of the man's skull, silencing his cries.

The Iron-Father launched himself at a group of Shinarii who were threatening to pull down the limping Brother Betorin, his bionic right leg still restricting his mobility following the damage it had suffered on the plague-cursed forge world. Gdolkin's blazing power axe did for one of the creatures, slicing his head off above the jaw. His bolt pistol stowed away, the Iron-Father pulled another man off Betorin, dislocating the cultist's shoulder as he did so. At the same time Gdolkin's servo-arm took hold of another grappling Shinarii and snapped his attacker's neck.

He was almost there; he was almost upon the Word Bearers. Gdolkin hefted his power axe in both hands, preparing to bring it down on the Dark Apostle in a scything sweep. Five steps - powerful leaping strides - no more, and he would be on top of the corrupt Chaplain.

But at that moment, the Word Bearer's demagogue completed whatever evil ritual he had been performing.

A crack like a thunderclap shook the cavern, knocking the Iron Hands as well as their assailants to the ground at a stroke - but that was only the beginning. The curious light that illuminated the caves began to fade.

Gdolkin scrambled to his feet, his eyes on the Dark Apostle. The blasphemer had his arms outstretched towards the obelisk, a bolt of blinding light streaming from his fingertips at the octahedral prism structure. As the light poured from the Apostle's hands the cloak of darkness shrouding his body burnt away. Where the stream of warp energy struck, the smooth glassy black surface of the stone pillar started to ripple and warp. The artefact began resonating, giving out throbbing waves of sound and kinetic energy. The ground began to shake in sympathy and then, with a granite cracking, chunks of rock started to come away from the dome of the cavern roof.

Gdolkin found himself staggering and stumbling to keep his balance. He could see that the Dark Apostle was shaking too but somehow kept rigidly upright, despite the waves of energy buffeting him.