There was a score of melta bombs, keyed to a single detonator, placed on the nexus when the company moved on. The junction was that big. The Blood Angels moved down the next tunnel, retreating from the blast they would unleash, and advancing on the foe. Raldoron ordered Sergeant Vahiel to hold the rear, trigger the detonator and note the results. The noise of the daemons was deafening, though still subsumed to the song of the manufactorum, but they were not yet in sight when Vahiel set off the bombs.

‘Detonation,’ Vahiel reported. ‘It looks like–’

The sound that cut him off was greater than the explosion. Sanguinius heard the deep-throated thunder of the blast. He pictured the nexus shattering, the conduits flying back in shards as the energy they transported was unleashed when the melta bombs ruptured their integrity. That was the material explosion. It was barely audible beneath the other sound. That sound, the one that silenced Vahiel and daemons alike, was the sudden wail in the heart of the song. The symphony of the manufactorum broke into a momentary cacophony. The words crumbled before they could finally be spoken. A mountain screamed. The dark miracle that fed the great gate above the planet stumbled in its operation. Even Chaos could be disrupted, and it was now. The shriek of the music ended quickly. Junctions elsewhere took on more labour, and the work of destroying reality resumed.

In the space of those few seconds, though, for the duration of the wail, Sanguinius felt the complex shudder like a stabbed animal. The pain went deep, much further than the immediate vicinity of the nexus.

After the shriek, the mournful insanity of the song resumed. From the rear came the rumble of collapsing stone and metal.

‘The chamber is gone,’ said Vahiel. ‘There’s been a major collapse.’

Sanguinius voxed the captains of the other companies. ‘Our strategy is bearing fruit. Destroy the large junctions.’ The desert scorpion of Baal was a juggernaut in its armour. A single spear could do nothing against it. But strike it with many, and it would fall. Enough spears would kill the foundry too.

‘We have our prey,’ Amit responded. ‘You will hear our blow very soon.’

The tunnel split ahead, the equally large branches turning left and right. The left-hand path took a steep descent. The roaring of the daemon horde came from there. Sanguinius chose it, wondering why there was still no sign of the foe. The Blood Angels had travelled two miles since the first blast. The volume of the howls was no longer increasing.

‘Lord primarch, are they retreating?’ Azkaellon asked.

‘It doesn’t sound as if they are, does it?’ said Sanguinius. It was more likely an auditory distortion created by the web of tunnels. There was so much unnatural about the manufactorum, a deceptive quality to the sound would hardly be surprising.