Each behemoth was a hydrogen-plasma mining station that drank deeply of the planet's violent atmosphere and refined it into valuable fuels used by the tanks of the Imperial Guard, the ships of the Navy and virtually every machine tended by the Adeptus Mechanicus. They were largely automated, as the handling of such volatile fuels was, to say the least, highly dangerous.
For several hours, and at the cost of scores of servitor drones, the first of the huge refinery ships was slowly dragged from orbit, its vast bulk moving at a crawl into the darkness of space.
Despite the danger of working in such a hostile environment, the work to moor the tug ships to the second refinery was achieved in little under three hours and it moved to join the first on the journey to Chordelis. The Adeptus Mechanicus magos overseeing the mission to Yulan was pleased with the speed with which the operation was proceeding, but knew that time was running out to recover the third refinery.
Already the tyranid fleet had reached Parosa and was heading this way.
Time was of the essence and a further six, frustrating hours passed as the tug crews tried again and again to attach themselves to the last refinery in the turbulent lower atmosphere. The tug captains moved in again, their frustration and orders for haste perhaps making them more reckless than was healthy.
But haste and a billion-tonne refinery packed with lethally combustible fuels are two things that do not sit well together.
The captain of the tug vessel Truda moved his vessel gingerly into position on the forward docking spar of the last refinery, eschewing the normal safety procedures regarding proximity protocols. As the Truda moved into final position, her captain was so intent on the docking lugs ahead that he failed to notice the Cylla coming around a sucking, gas intake tower.
At the last second, both captains realised their danger and attempted to avoid the inevitable collision, the Truda veering right and barrelling into the intake tower. She smashed herself to destruction against its structure, buckling the hot metal of the tower and crashing through the thin plates before exploding as her fuel cells ruptured.
The Truda could not have struck the refinery in a worse place: designed to capture the hot gasses from the planet below, the intake tower sucked a huge breath of the tug's explosion, carrying the burning plasma of its engines to the very heart of the refinery's combustion chambers, where it ignited an uncontrolled chain reaction.
Emergency procedures initiated, but blast doors not shut since the refinery's construction thousands of years ago jammed and shutdown measures failed as ancient circuits failed to close, their wiring long having since degraded to the point of uselessness.
Within minutes of the crash, the internal chambers of the refinery began exploding sequentially, with each blast blowing apart more storage chambers and multiplying the force of the blast exponentially.
From high orbit, it appeared as though the giant refinery was convulsing and before any warning could be given to the ships still clustered nearby, it exploded in a flaring corona that eclipsed the brightness of the system's star.
Everything within a thousand kilometres of the blast was instantly vaporised and the Shockwave ruptured the surface of the planet below, sending plumes of fiery gasses into space.
The blast wave faded, leaving nothing of the refinery or the hundreds of men that made up the Adeptus Mechanicus detachment tasked with its retrieval, save an expanding cloud of burning plasma gas.
Oblivious to the disaster in their wake, the flotilla of tugs continued onwards to Chordelis with the two surviving refineries lifted from geo-stationary orbit around Yulan in tow.
Why the Ultramarines' admiral had tasked them with this dangerous duty, they did not know, but theirs was not to question, simply to obey.
The six trucks sat silently in the dimly lit vehicle hangar, moonlight streaming in through the high windows providing the only illumination. A dozen soldiers granted as they loaded crates onto the back of the trucks, overseen by a supply sergeant of the Erebus Commissariat, who, despite the fact that the temperature was below zero, sweated beneath the fur-lined hood of his winter coat.
He smoked a limp bac-stick and stamped his feet to ward off the cold as the last crate was loaded onto the truck, each one marked with a scorched burn where a Departmento Munitorum shipping number and regimental crest had been stamped. The tailgates of each track were slammed shut and secured with chained locking-pins and as his soldiers filed passed him, he pressed a wad of promissory notes into each one's hand.
'Don't do anything dumb with this,' he warned.
As the last of the soldiers left the garage, he stubbed out his bac-stick and circled the tracks, checking that all the tailgates were secured. As he rattled the last one, a group of figures emerged from the shadows at the far end of the garage.
'You all done?' asked the figure at the front.
The supply sergeant jumped, his hand reaching for the pistol below his coat.
'I wouldn't do that if I was you,' growled a hulking figure behind the first and the sergeant raised his hands.
'Snowdog,' he breathed in relief, lowering his hands as the group came into the light. He flipped another bac-stick into his mouth.
'You expecting someone else, Tudeca?' asked Snowdog, his shotgun resting on his shoulder. The leader of the Night-crawlers wore a thick woollen coat to ward off the winter's chill and his bleached hair shone as silver as that of the girl beside him. Behind Snowdog stood the psychotic thug he called Jonny Stomp and a trio of painfully thin youths decorated with colourful, if badly drawn, tattoos across their faces. At a gesture from Snowdog, they jogged towards the cabs of three of the tracks, a redheaded girl in a tight catsuit climbing into the nearest one.
'No,' said Sergeant Tudeca. 'It's just you startled me. I wasn't expecting you so soon.'
'What can I say: I like to surprise people,' said Snowdog, nodding to Jonny Stomp. The brutish giant climbed onto the back of each of the trucks in turn, counting the number of crates in the back of each one. Sergeant Tudeca stepped nervously from foot to foot, surprised Jonny Stomp could count past his fingers, as Snowdog and Silver watched him carefully.
'It's all there?' asked Snowdog.
'Yeah, it's all there. Medical supplies and ration packs, just like you wanted. Didn't I tell you I could get them for you?'
'Yeah, you really came through for us,' agreed Snowdog, putting an arm around Tudeca's shoulders and lifting the pack of bac-sticks from his breast pocket.
Snowdog waited for a second, raising an eyebrow until Tudeca took the hint and lit the bac-stick for him, the flame wavering in his shaking hands. Snowdog reached up to steady the sergeant's hand.
'You okay, Tudeca?' said Snowdog with false concern. 'You look all jittery, man. Something on your mind?'
'It's going to cost more,' blurted Tudeca. 'I had to give my lads twice what they normally get for this. The commissariat provosts are coming down hard on anyone they catch stealing, and if they arrest me, it's a bullet in the head for sure.'
'Tudeca, Tudeca,' soothed Snowdog. 'Don't look at this as stealing: look at it as redistributing it to the people who really need it. Look, all this stuff was going to the medicae buildings for the regiments from off world. I'll make sure it gets to the people of Erebus… at a nominal charge.'
Tudeca laughed, a hoarse bray, and said, 'Nominal charge! You'll be selling this for four times its worth.'