Dan Abnett - Know no fear. The Battle of Calth

But this desecration, this takes his casus belli to a whole new level. This is not a just war, this is a war crime. It defies and shames the codes and precepts of the Legiones Astartes, codes and precepts set down by the primogenitor Emperor. The Word Bearers have perverted any semblance of the true and legal path of the Imperium, or the moral code of mankind.

Here and there, Ventanus spots signs that have been daubed on walls, presumably in blood. Eight-pointed stars and other devices he is not familiar with, and the sight of which make him uncomfortable.

Over the chug of the speeder’s engine – a chug that is developing a worrying, clattering under-note – Ventanus can hear the rattle of other gun-carriages moving through the nearby streets. They are in the industrial hinterland between the starport proper and the city. Ventanus is desperate to find a route that they can use to break out and head north-west to Erud. His primary concern is re-establishing contact with his company and the other units in the Erud muster. If they’ve come through this intact, or approximately intact, he intends to make them the spearhead of a counter-strike.

A haze washes across the city and the port. It’s smoke, in vast quantities, but it’s also vapour. Steam. A fog swathes the skyline, blanketing the river basin and turning millions of individual fires into soft orange smudges. Ventanus has seen that phenomenon before, when large bodies of water have been flash-evaporated by sustained energy discharge. A dead ocean condenses over the city lowlands.

They turn another corner, and see six Word Bearers advancing down the freight lane ahead of them. The Word Bearers challenge them, and then open fire.

The speeder rocks under the hits as it starts to reverse. Its armour is pretty solid, but Ventanus knows it’s taken quite enough punishment. He glides backwards, hoping to swing-turn on the hardpan in front of a fabricator shed and find another path. More Word Bearers open up on them, firing from an overwalk, and from a girder bridge between two manufactories. A mass-reactive round explodes against the side of the cab, where the roof is already peeled back and torn. The shock lurches Selaton hard.

They’re running out of ways to turn.

Ventanus reverses faster. He runs down two Word Bearers who emerge behind them. Their crimson-armoured forms are slung out from the repulsors at the speeder’s plated back end and fall, bouncing and clattering across the rockcrete.

But he can’t simply run down the gun-carriage that’s rolling out, facing their back end. It’s twice their size, twice their mass, and it starts traversing its quad-guns to target them.

‘Go!’ Selaton shouts. ‘Go! Through them!’

Ventanus kicks the speeder forward again, cranking thrust. He knocks down one of the Word Bearers they have already smashed aside once. The brute was regaining his footing. The right front wing catches him hard, folds him around the reinforced fender, and tosses him sidelong. He tumbles, and lands in a way that speaks of a severed spinal cord.

Selaton rises in his seat, bracing the autocannon against the sill of the screen. They’re heading directly for the Word Bearers squad that cut them off in the freight lane. They’re also running right through the hail of fire chopping down from the overwalk and girder bridge. Shells slam into the ground around them, pluming fire and grit. Others thump the bodywork like piledrivers.

Selaton kicks off with the cannon. He gets a good angle, given the improvised circumstances, and stitches a line of shots along the girder bridge, ripping handrail spars and shredding the metal balustrade. He knocks two of the enemy shooters off their feet, and then licks across a third. Ventanus sees a helmet explode like a red paint flare. The casualty rocks backwards off the bridge and hits the ground a second after they’ve passed underneath.

Selaton drops his angle and guns down one of the ground troops. The rotating cannon chews the figure up, shredding him like a sack of meat and metal chaff. The others stand their ground, firing straight at them. Ventanus, his grip unflinching, sees a mass-reactive round pass through the cabin between his head and Selaton’s and exit through the back port-slot.

He knocks one Word Bearer down, throwing him over the racing speeder. Then he hits another and catches him on the speeder’s plated fender, upper body spread across the nose, legs caught under the machine. A huge wake of sparks kicks out from the underside of the speeder as it carries the road kill along, abrading the heels and calves of the pinned Word Bearer’s heavy Mark III battle plate. There is a terrible noise of squealing and scraping. Ventanus can’t dislodge the man.

A wall collapses into the freight lane ahead of them, and a crimson Land Raider lumbers into the open, its hull tipping up and over the rubble of the demolished structure. It swings around, weapon mounts lining up.

Ventanus peels left. There’s no other practical. He rams the sheet metal wall of a warehouse unit and blows clean through it to escape the Land Raider’s hail of fire. The Word Bearer pinned to their front end takes the force of the impact. If he wasn’t dead already, he is now.

But so is the speeder. The impact has killed the drive reactor. It starts coughing and rasping, leaking smoke from its vents. The speeder coasts to a halt in the darkness of the warehouse.

Ventanus and Selaton dismount. Selaton has the autocannon and the last of the ammo hoppers. Ventanus gets the standard, and then pauses and goes back to prise the boltgun out of the dead grip of the Word Bearer now all but fused into the mangled nose. There’s very little of him intact from the waist down. There’s a smell of superheated metal, of friction, of cooked bone marrow.

The first of the Word Bearers force their way in through the gap the speeder created. Selaton rakes them, cutting two down and sewing more holes in the wall for the light to shine in.

His hopper is spent. He ditches the cannon and pulls his boltgun.

They start retreating across the jumbled floor space of the warehouse, trading shots with the Word Bearers who are breaching their way in through the gap. Bolter shells spit to and fro. Ventanus scores a hit, but he can’t be sure if it’s a clean kill. Sheer weight of numbers is stacked against them.

He keeps expecting a wall to cave in and the Land Raider to storm the barn, hunting for them. He can hear it outside, rumbling and revving.

Suddenly, there’s a staggering explosion outside. A brilliant light-flash pushes into the warehouse for a second, through every slit and bullet hole and window. The buildings shake, and whizzing pieces of superhot machine parts and plating debris punch through the wallskin.

Ventanus and Selaton pick themselves up. The Word Bearers who have forced entry after them are getting up too. They attempt to re-lock target finders on the fleeing Ultramarines, but they are bewildered. What was the blast? Did something just kill the Land Raider?

Searing plasma beams chop the gloom and slice them apart as they turn. The beams – scintillating green – fuse through and through blast holes in their armour and pop their helmets like balloons.

Ventanus and Selaton back into cover, weapons ready.

Lugging their powerful, close-quarter plasma blasters, skitarii of the Mechanicum flood into the building. Without compromise, they finish off any of the Word Bearers not cleanly killed.

There are dozens of the fearsome Mechanicum fighters.

‘Warriors of the XIII,’ one of them broadcasts in loudhailer mode. ‘Make yourself known to us. Hurry, time is against us.’

Ventanus gets up, raising the battered standard.

‘Remus Ventanus, 4th Company,’ he announces.

The skitarii commander comes to face him. He’s a big veteran, scarred and ugly, gaudy in his aposematistic wargear. One of the red eyeslits in his copper visor is flickering.