The victories were bloody, but small and insignificant when compared to the larger conflict.

Across the entire Urgall Depression, hundreds of battles between legionaries were being fought. Some were company-strong, others were squads or even individuals. There was no scheme to it, just masses of warriors trying to kill one another. Most of the loyalist troops had moved on from the dropsite and were engaging Horus’s rebels at the foot of his fortifications, but a few still occupied this beachhead. Scattered groups of traitors had spilled out as far as the dropsite but were quickly destroyed by the troops holding it. These were skirmishes, though, and nothing compared to the greater battle.

Death Guard forces were spilling out of their tunnels now, and roamed down the slopes, bolters chattering. One of the reconnaissance company, pausing to sight down a sniper rifle, took a lucky shell in the neck and crashed back into a trench. Apothecaries moving amongst the Legion army were already hard-pressed, and the lone sniper was lost in the morass before help could reach him.

Knowing his men were taking fire, Nemetor had his company rise up to meet the counter-attacking Death Guard and the lower hillside was instantly swamped with clashing, armoured bodies. Close combat and short-range firefights erupted in their hundreds and the ridge practically undulated with their furious ebb and flow.

Tramping over the scorched remains of the Death Guard brought down in the inferno from Vulkan’s gauntlet, Numeon and his brothers kept to the middle trench and soon found themselves reunited with their primarch.

In a brief moment’s respite, Vulkan stared to his left in the direction of a distant battle where the Morlocks fought and died.

‘Ferrus drives hard up the centre,’ he said as Numeon drew to his side. The Pyre captain had followed his primarch’s gaze but could not discern Lord Manus amongst the embattled warriors.

‘It is as I feared, Artellus,’ Vulkan went on, lost briefly in remembrance. ‘He acts without thought or concern.’

Varrun gave Numeon a questioning look.

‘It is a private matter,’ he hissed curtly, making clear that was an end to it.

‘I would not have him fight alone,’ said Vulkan, ‘but nor should we give up what we have bled to obtain. Have K’gosi maintain position here. The Pyroclasts will hold the breach and this section of the trench. Relief is coming and we must be ready to clear the way for it when it does.’

Numeon gave a quick nod and saw it done. He also saw Nemetor and the 15th still driving up the ridge, becoming stretched. By now, the bulk of the Firedrakes were deep inside the trenches and coming up in support.

‘Nemetor,’ voxed Numeon, ‘you are pulling your company out of position. Regroup and return to the command battalion. Firedrakes are inbound.’

Nemetor was quick to reply. ‘ The Death Guard are on the run. Have switched to short-scopes and blades. If we pursue now we can destroy them so they can’t regroup.’

‘Denied, captain. Pull your forces back.’

‘ I can press the advantage, brother.’

Nemetor had ever been a fierce warrior. He drove his troops hard, leading by example, and smashed into the fleeing first defenders with irresistible momentum. Short-scoped, the legionary sniper rifle was deadly and incredibly powerful. It was a credit to Nemetor’s company that they could adapt their tactics so fluidly in the face of opportunity. At short or long range, the Reconnaissance Marines excelled, but if they kept pushing it would get them all killed or overrun.

Numeon was about to give the captain a direct order to fall back and regroup when he saw something in the distance that made the words catch in his throat.

Rolling down the slope was a dirty cloud, too thick and too low to be fog. It spilled into the myriad trench-works, funnelled by the conduits of hewn earth.

And it was fast. In seconds it had cleared the no-man’s-land between the previous trench and the next bank of fortifications and was hurtling at Nemetor and his warriors. It overtook the Death Guard first, who adjusted respirators before the miasma hit as if they knew it was coming.

Which, Numeon realised, they did. The retreat was a feint, a trap, and Nemetor’s company were in it.

‘Gas!’ cried Numeon, but by then it was too late. Though the other legionaries switched their respirators to maximum filtration, Nemetor and the bulk of his company were engulfed before they could act. Still chasing down the retreating warriors, they suddenly found themselves enveloped by a poison cloud and surrounded by rapidly regrouping Death Guard.

The Legion armoury was vast, and not all of its weapons were as obvious as a bolter or as noble as a sword. There were those who wielded devices of much more insidious potency – the slow and agonising ones, the weapons that forever scarred both the bearer and the victim. They did not discriminate and made no allowance for even the strongest armour. From the vaunted champion to the lowliest mortal, they were the great levellers and their works were terrible to behold.

Numeon saw them now and swore an oath that he would kill the one that had unleashed such terror on another legionary.

Whatever contagion the Death Guard had used, it was potent. Moreover, it had been designed to be specifically effective against the Legiones Astartes. Through the breaks in the cloud where the dirt-haze thinned to a sickly, sulphurous yellow, Numeon saw his brothers dying. Power armour was little defence against it. The few that had managed to engage their respirators would perhaps last a minute, maybe more, but the rest were dead men. Metal corroded against the cloud’s necrotic touch, rubber mouldered and split, flesh and hair burned. More than a hundred of the reconnaissance company collapsed, choking and spitting blood. Dozens more were hacked apart or shot down by resurgent Death Guard attacking in the confusion.

Igataron went to wade in, the cloud still creeping down the slope and less than fifty metres away, but Numeon stopped him.

‘We gain nothing by condemning ourselves too,’ he said, then voxed to one of the pilots riding strafing runs across the battlefield. ‘R’kargan, bring your bird in on our position to blow away some of this filth.’

R’kargan replied with a clipped affirmative before seconds later a throbbing engine sound came into sharp focus above. Several of the reconnaissance company looked up at their salvation as R’kargan brought the gunship low. Turbines burring, the Thunderhawk’s downdraught hit the cloud and spread it out, reducing its potency, if not dispersing it completely.

The gunship was rising again, returning to strafing altitude, when a missile caught its left wing and sent it reeling. A whip of black smoke unfurled from its damaged engine, coiling up and then back upon itself as R’kargan was forced to bank. He crashed into the side of the ridge a few moments later, the gunship’s fuselage torn up and burning. Scurrying from their holes, the traitors were quick to fall upon it.

There was no time to mourn. R’kargan had made his sacrifice and saved what was left of the reconnaissance company. Now those that yet lived had to make that worth something.

‘To your brothers!’ roared Vulkan and stormed up the ridge. He let off small gouts of flame from his gauntlet, burning back what pestilence remained to further weaken its effects. The Pyre Guard followed, ploughing into the slowly dissipating cloud, turning the scales back into the Salamanders’ favour and breaking their beleaguered company brothers out of the trap.

Many of the 15th didn’t wear battle-helms, preferring to be unencumbered for the stealth work at which they excelled. These warriors had suffered the worst. Skin sloughed away by virulent acids, ravaged by pustules and choking on vomit, eyes drowning in pus from the dirty bomb, there was almost nothing left of them but half-armoured carcasses. As he drove hard into the few remaining Death Guard who had attacked inside the cloud, Numeon heard something scraping at his leg. He turned, glaive angled to thrust downwards, expecting to face a desperate enemy, but instead saw a dying Reconnaissance Marine. Blood was trickling freely from the ruin of the legionary’s mouth, sticking to his chin and neck in a viscous film. The dying legionary grasped feebly at Numeon’s greave. His fingers had been reduced to stumps, the tips of his gauntlets eaten away, and he left ruddy tracks in the metal. He was trying to say something, but his vocal cords were all but liquefied and the sound that came from his mouth was an agonised gurgle.