'Come to new heading, zero-five-seven,' ordered Tiberius. 'Flank speed. We've got to get past their cordon.'

The entire bridge groaned as the battered ship forced itself into the turn, her buckled keel squealing in protest.

'Come on, hold on.' Tiberius whispered to the spirit of the Vae Victus.

Sprays of ichor burst before his ship as the bombardment cannon's shells impacted on the kraken's hide, detonating in a giant fleshy burst of gore. An angular prow slid into view as the Mortis Probati crossed the bow of the Ultramarines' ship. Her starboard guns hammered the listing remains of the kraken, blasting its thrashing body to expanding clouds of scorched flesh.

The second kraken ponderously moved to engage the Mortifactors' ship, its blade wings rippling as it changed course. Behind it, Tiberius could see the outline of one of the massive hive ships, limned in the glow of the planet's atmosphere.

'All ahead full,' shouted Tiberius. 'Twenty-degree down angle. Take us through the gap!'

Tiberius gripped the cracked timbers of his command pulpit as the Vae Victus shook violently and accelerated through the gap the strike cruisers had blasted.

Smaller drone creatures peeled off from their attack on the Sword of Retribution, swooping around to come for Tiberius's vessel.

'Lord admiral!'

'I see them, Philotas. Engage with port batteries.'

'We won't hit much without the targeting surveyors.'

'Fire anyway.'

'If they board us, we will be unable to repel them.'

'Damn them! Our only priority is the hive ships. Stay on target!'

The Sword of Retribution pushed deeper into the swarming tyranid creatures, firing devastating broadsides from its many gun decks, filling the space around it with vast explosions. It had suffered the least of the Imperial fleet and its captain had volunteered to take the lead position in the attack.

Lethal strikes from the dorsal lances punched a hole in the tyranid fleet through which the smaller vessels of the fleet sailed. Alien vessels surged to close the gap, but the Space Marine vessels were too fast, slipping past the vanguard organisms on a course for the hive ships.

The Kharloss Vincennes limped behind the Sword of Retribution, her ruptured hull and damaged engines causing her to fall behind the speeding Space Marine ships. As the tyranid creatures closed the gap in their forces, they also closed inexorably on the wounded carrier. Unable to launch fighters or bombers to defend herself, she was easy prey. Close-in turrets and broadside batteries kept the alien creatures at bay for a time, but as more and more closed with her, there was no doubting the outcome of the battle.

Snaking tentacles drifted forwards from a dozen cone-shaped drones, latching limpet-like to the hull of the battling carrier. Acidic secretions bound the creatures to the ship and their maws irised open, revealing caverns of giant teeth that burrowed into their prey at a horrifying rate.

Larger ships closed, then suddenly altered course to head back towards the planet, recalled by the hive mind to catch its attackers in a trap.

As the Kharloss Vincennes fought the losing battle for its life, the remainder of the Imperial fleet pushed on into the swarm.

The nearest hive ship lay before the Vae Victus, its gargantuan shape filling the viewing bay before him. Attendant guardian creatures formed an impenetrable barrier between her and her escorting ships.

'All ships, fire all weapons!' shouted Tiberius. 'We have to break through.'

Massive projectiles hurtled through space, exploding in vivid blossoms of fire ahead, but none were reaching their target. Kraken and drones moved in an intricate ballet that would have been virtually impossible for the Imperial Navy to emulate, screening the hive ship from the incoming firepower. Tiberius saw a handful of shots penetrate the living shield, but precious few were causing any real damage.

Tiberius opened a vox-link to the captain of the Sword of Retribution.

'Captain, you must clear us a path! Use whatever means are necessary.'

He snapped off the link without waiting for an answer and said, 'Philotas, try and raise Uriel. Tell him that whatever he's doing, he'd better do it fast, because we won't last much longer here.'

Rain hammered the mountainside and lightning provided stroboscopic illumination across the rocky slopes as the thousands-strong horde scrambled up towards the bunker. Rivers of foaming water flooded downhill, sweeping great swathes of the aliens with it.

For once, the tyranids' metamorphosis of a planet's surface was working against them, saw Uriel. The glutinous mud was as much of a hindrance to them as it was to the Space Marines. Bolter fire raked the slopes, blasting apart hormagaunts and other nameless horrors in stuttering blazes of shells. Uriel hurled a pair of grenades, ducking back behind a rock as they detonated, sending up showers of mud and alien body parts.

Screeching carnifex struggled in the mud, their bulk causing them to sink knee deep. The winged monster flapped above the horde, buffeting winds keeping it from advancing for now.

The Deathwatch picked off aliens with single shots to their vulnerable organs, careful to conserve their ammunition. Bannon scrambled across the slopes to Uriel's position, his armour caked in clods of mud, the symbol of the Imperial Fists barely visible.

'They're circling around behind us. We need to get inside!'

Uriel looked up into the filthy downpour, seeing indistinct shapes bounding across the rocks towards the bunker. Bannon was right, given a few minutes, they would be surrounded.

'Let's get going then,' he said, rising from behind the rock.

Uriel felt the ground shift under his feet and leapt backwards as a huge portion of mud suddenly detached from the slope, sliding downhill as the torrential downpour washed it from the side of the mountain. He landed on his back and rolled, grabbing onto the rock as he felt himself slipping. His bolter clattered behind the rock.

He heard Bannon cry out and saw the captain of the Deathwatch desperately scrambling in the mud to keep from sliding into the mass of aliens below. Uriel braced himself on the rock and held out his hand towards Bannon. The two warriors gripped wrists and Uriel began pulling.

'Uriel!' shouted Bannon.

He looked up, seeing a monstrous beast with a fang-filled maw clawing its way up the slope. Its long, taloned fist clamped around Bannon's ankle and squeezed. The ceramite cracked under its awful strength and its black eyes locked with Uriel's. Bolter shells burst around the battle as the Deathwatch bought time for Uriel to rescue their captain.

Uriel roared as he fought against the tyranid's strength, knowing that he could not defeat it. Bunching the muscles in his thighs, he braced his boots against the rock and gave a herculean pull, reaching down to sweep up his bolt-gun with his free hand.

Feeling the tendons in his arm crack, he straightened his legs, the counterbalance of the tyranid warrior pulling him to a standing position. Gripping his bolter in one hand he aimed at the creature's head.

'Let go,' he said simply and emptied the magazine into its face, its brains mushrooming from the back of its skull as his bolts detonated within its cranium. Its grip spasmed and Uriel hauled Bannon to the rock, pulling him to his feet as another streak of lightning lit up the sky.

The two Space Marines slipped and stumbled their way towards the bunker through the torrents of water and mud. Twice, tyranid creatures came close to overtaking them, but each time the unerringly accurate bolter fire of the Deathwatch kept the aliens at bay. Uriel heard static-filled words in his helmet vox, but could make little sense of them. He recognised the voice as that of Philotas, the deck officer of the Vae Victus, but whatever he was saying was unintelligible.