‘Monsters,’ Kade answered at last, snugging the cannon into the crook of his arm and raising the twinned muzzles.

Har’gaan shouted up to Za’tenga and Illion.

‘Run!’

But his voice was eclipsed by tectonic thunder.

Ba’ken’s grim humour faded when he saw Va’lin had not trained the monocular on the canyon wall as instructed. ‘Va’lin,’ he said.

The Scout seemed not to hear. He had the lens aimed at the distant horizon line and the chain of volcanoes that towered across it. Largest of them was Deathfire, and she looked angry.

‘I see something…’ Va’lin began.

Ba’ken followed the Scout’s gaze. His eyes widened. ‘It’s a helstorm.’

Nocturne was a volatile world, the overbearing gravity exerted by its larger moon created an environment of tectonic fragility. Earthquakes, volcanic eruptions and pyroclastic storms were all common. Helstorms were amongst the worst of those devastating natural events. It was not the potentially world-ending Time of Trial but it was destructive, deadly to any caught without shelter, and it was happening. Now.

Deathfire vented spears of cloud and gouts of debris from the caldera at her peak. Heartblood, the life of Nocturne, was running down her flanks in runnels of fire. A sudden explosion shook the summit, rippling outwards in a shockwave. It began as motes of sand-ash, vibrating against one another and grew into a temblor several minutes later that trembled the earth beneath Ba’ken’s feet. In the same moment, a great spume of pyroclastic gas and smoke erupted as Deathfire roared into the flame-scarred heavens, nearly blotting out the sun. She was not finished, not nearly. She was merely warming up, fashioning an altogether more violent encore to the first refrain.

It hit seconds later, though Ba’ken and the others had to wait minutes to feel the effects, an immense quake that cracked the Scorian Plain in chasms, the fractures many and wide-ranging. Flame, intense and angry, spewed up from every fissure and the view down into the canyon was lost behind a sudden wall of conflagration.

Ba’ken sent the Scouts back. Hot hail was raining from the rapidly blackening sky, deadly to warriors only armoured in carapace. He grimaced as he opened the comm-feed in his gorget, pulling a chunk of rock from his vambrace and wincing at the burning line scorched across his cheek at the same time.

‘Forge Master,’ he said into the feed, attempting to raise the Techmarine monitoring their progress in the Prometheus moon far above Nocturne’s turbulent atmosphere.

Behind him the two Scouts were regaining their feet but stayed low and wary as the hail continued. They were right at the edge of its destructive fury.