Trains had been arriving daily for the past month, each laden with frightened farming communities from the outlying regions and, as the largest city on Tarsis Ultra, Erebus had been receiving the majority of these refugees. As if the city wasn't crowded enough already. Pren shrugged, pushing his way through the crowds and making his way to the control booth that overlooked the platform.

Seventeen train berths and fifty track lines radiated from the docking bays. He and his staff of seventy men had pulled double shifts for the last two months, ensuring that each train had deposited its human cargo and then departed on time to pick up yet more. It was thankless, dirty work and there was precious little reward to be had, but it was the life the Emperor had chosen for him and though he knew it would do no good to complain, Pren Fallows was not the kind of man to let that stop him.

Powerful arc lights mounted on steel towers bathed the platforms in a ghostly white light, and despite the heat, his breath fogged before him. Yellow coated provosts from the city Commissariat directed people from the docking station, taking names on clipboards and directing them to the Ministorum camps further up the valley.

It was a scene of organised chaos, but this train had been the last of the day and there were no more scheduled until noon the following day, which would allow Pren and his crew to enjoy a well-earned break.

As the provosts escorted the last of the refugees from the station, a blessed calm descended. Pren stopped and smiled, enjoying the dead quiet of a winter's night and an empty station.

He climbed the rusted iron ladder to the control booth, stamping the slush from his boots before pushing open the door.

'Close the damn door!' shouted Halan Urquart, his deputy controller, who sat before a bank of controls, his feet up on the table, drinking a cup of hot caffeine. 'You're letting all the damn heat out.'

'Sometimes I wonder if you understand who's in charge here, Halan,' replied Pren, unfastening the wax-lubricated zipper on his winter coat and hanging it on a hook on the back of the door.

'Yeah, I wonder that sometimes too.'

'Anything to report?' asked Pren, brushing the ice from his beard.

'Nah, it's been real quiet. The provosts seem to have finally got the hang of moving people out of here without bothering us.'

'About bloody time,' commented Pren, pouring himself a mug of caffeine. It was lukewarm, but beggars couldn't be choosers. He pulled up a seat next to the window, watching as another flurry of snow began to fall, coating the platforms in a fresh blanket of pristine white.

Pren lifted the station logs from the basket tray beside Halan and began flicking through his deputy's scrawled handwriting. He sipped his caffeine, noting that the turnaround times for the land trains was as quick as it had been even before the war. He'd need to remember and say a few encouraging words to his staff come the morning.

He flipped over to another page, glancing up as a shiver passed down his spine. He put down his mug and stared out the misting window, squinting through the fogged glass at the twin pinpricks of light that were approaching the station.

'What the hell…' he muttered.

'What's up, chief?' asked Halan.

'Look,' said Pren, pointing in the direction of the mysterious lights.

'What the hell…' said Halan.

'I know,' said Pren. 'I thought we were all done for today.'

'We are, I don't know what that is.'

The men watched as the two points of light drew closer through the night's darkness, their sense of apprehension growing with their brightness. As the lights got closer, they came within the glow cast by the tower lights. Halan and Pren both breathed a sigh of relief as they saw the sleek shape of a land train glide smoothly into the station, its sides and roof coated in a thick layer of frost.

The train slowed and came to a complete halt at the end of the furthest platform, its doors jerkily sliding open. Pren and Halan waited for the inevitable crowds to emerge, but nobody disembarked from the train. It simply sat, silent and unmoving on the far end of the platform, steam venting from the grilles around its engines and the track.

Both men shared an uneasy glance.

'I guess we should go down and have a look,' suggested Pren.

'I just knew you were going to say that,' said Halan, pulling on his winter coat and gloves.

Pren grabbed a portable illuminator and donned his winter gear, following his deputy outside into the biting cold. He clambered down the frosted ladder and trudged alongside Halan through the fresh snow towards the unmoving land train. As they drew nearer, they could see the windows of the train were dark and opaque with frost, even those of the driver's cab, and their sense of unease grew stronger.

The darkness and silence of the docking station, normally a relief after the hectic bustle of a day's work now pressed in around them and Pren wished some of the provosts were still left in the station. At least they were armed.

He gripped Halan's arm and the man nearly jumped out of his skin.

'Guilliman's oath!' swore Halan. 'Don't do that!'

'Look, you can see the train's number on the engine.'

'So?'

'Well we can tell which bloody train this is and why it's here now, you idiot.'

'Oh, right,' said Halan, pulling out a data-slate from his coat and scrolling through a list of numbers, eventually stopping at the train's designation.

'Got it. This was due in last week.'

'Last week? And no one noticed it was missing?'

'I guess not, we've been pretty busy here you know.'

'True,' said Pren. 'Well, where's it come from?'

'According to this, it was under the supervision of a Lieutenant Quinn from the Logres regiment. They were picking up refugees from across the north-eastern districts. Their last stop was at Prandium and they should have been here six days ago. I guess the train must've come in on auto.'

Halan tucked away the slate and the pair gingerly continued towards the train, their steps cautious, hearts beating faster. The train's doors stood open, but still no one got off. A light flickered inside, briefly illuminating the train's interior and a tinkle of broken glass made both men jump.

Steam gusted from the engine, melting the ice coating the train and cold water dripped from around the opened doors. Pren and Halan reached the doors and warily stepped into the darkness of the train.

Pren flicked on the illuminator and swept the beam around the interior of the carriage.

He heard Halan cry out in horror and fell to his knees as his mind attempted to cope with the butchery he saw all around him.

Bodies. Hundreds of gutted, flensed, dismembered and partially devoured bodies filled the carriage, like hunks of meat in a coldroom. Strung from the walls on resinous streamers of glistening mucus, their dead flesh hard and unyielding, their frozen eyes staring down in mute accusation at the station operators.

Stalactites of frozen blood reached down to the uneven floor and Pren felt a suffocating fear swell in his chest. He dropped the illuminator and it rolled down the carriage floor, casting lunatic shadows across the interior of the frozen charnel house, the spinning beam giving the rictus features of the corpses a hideous animation.

'Sweet Emperor—' wept Pren. 'What happened here?'

But the dead had no answers to give him, merely frozen eyes, emptied bellies, shorn limbs and gnawed flesh.

And further back along the train, a creature that had first come to Tarsis Ultra many months ago ghosted from its lair and vanished into the warm labyrinth of Erebus city.

The combined naval might of the Imperial defenders of the Tarsis Ultra system hung in orbit around the world that gave it its name. A chain of linked space stations ringed the planet's equatorial belt, towed into position to face the approaching tyranids by a host of tugs and pilot boats. Dozens of defence monitors and system ships lumbered into their position in the battle line alongside Admiral de Corte's flagship Argus, the battlecruiser Sword of Retribution, and the Dauntless cruisers Yermetov and Luxor.