'Damn me, but that was some fine shooting. My compliments to the gun deck.'

'Aye, sir,' replied the gunnery officer, proudly.

He watched the viewing bay, seeing the remaining enemy ships shuddering, as though gripped by some form of spasm.

'What in the Emperor's name is that?' he wondered aloud.

Before he realised what he was seeing, bolts of gelatinous liquid spurted from the front section of the bio-ships.

'All ships, hard to starboard!' he yelled, suddenly understanding what was happening.

The bridge of the Mariatus heeled sideway as emergency power was routed to the engines, but a ship of war does not react quickly, even if her captain does. With terrifying speed the bolts hurtled towards his ships, streaking through space in a tightly focussed stream. Payne gripped the armrests of his chair as his ship fought against her forward momentum to turn away from the incoming fire.

Even as the bolts slid to the side of the viewing bay, he saw that it would not be enough. The Mariatus would escape significant harm, but there was no way either of her sister ships could possibly evade in time.

Three corrosive acid bolts struck Heroic Endeavour on the lower section of her engine compartment. In panic, her Adeptus Mechanicus enginseers shut the engines down, venting her combustion chambers as they realised the acid was eating away at the plasma cells that powered the engines. Their quick thinking undoubtedly saved the ship and, to their immense relief, emergency procedures were able to halt the damage before the acids could breach the volatile fuel stores. Four hundred and thirty-seven men lost their lives in the attack, but her sister ship, Von Becken, was not so fortunate.

The full force of the tyranid weapons struck Von Becken broadside on, just behind her swept prow. The sheer force of impart smashed the bolts through the first layered sections of armoured panels, before the bio-acids ate through the remainder and the full force of the tyranid weapons engulfed the mid-level decks of the ship.

Hundreds died in the first moments of impact, smashed to pulp or sucked into space as explosive decompression blew out adjacent sections of the hull. The acids filled compartments with burning fluids that dissolved flesh and metal in a heartbeat, the fumes as lethal as any nerve agent devised by the Adeptus Mechanicus. Blast doors rumbled closed, sealing off the area of the impact, but the corrosive fluid liquefied the doors and spilled onwards, dissolving decks and pouring down onto the screaming men below.

The Von Becken's hull, already weakened by the acids and under stress from the violent manoeuvring screeched in protest, finally buckling as the venerable ship split in two.

Torpedoes launched from the Cobras of Hydra squadron streaked through space on blazing tail plumes, arcing for the nearest of the giant manta-like creatures. A cloud of spores drifted before the ship, and as the torpedoes closed the gap, a swarm of them surged forwards to intercept the missiles. Explosions rippled through the cloud of spores as the torpedoes smashed through them, some detonating prematurely, some broken apart by the acidic explosions of the spores.

Not all the torpedoes could be stopped and a handful slammed into the body of the mantis creature, the primary warheads vaporising a chunk of its hide, before the tail sections exploded, thrusting the powerful centre section of the weapons deep inside the creature to detonate.

The monster's belly heaved as the torpedoes exploded one after the other and it listed drunkenly as its lifeblood poured from its gaping wounds. But as grievously wounded as it was, the creature was by no means finished, and it could still fight back. A swelling of intercostal motion pulsed along the top of the creature and a flurry of jagged spines rippled from its flanks, thousands hurtling towards its attackers like enormous javelins. At such range, the odds of hitting a relatively fast moving target such as a destroyer were huge, but if you factored in the sheer number and density of the spine cloud the odds changed dramatically.

Two Cobras exploded as hundred metre spines hammered through their armour, smashing through the armaplas and ceramite hulls with horrifying ease. The lead vessel's bridge was destroyed upon first impact, penetrated from prow to stern by a dozen spines, while the second was reduced to a blazing hulk as three giant spines penetrated her engine core and started dozens of uncontrollable conflagrations.

The last vessel, shielded from instant annihilation by her sister ships, was nevertheless struck several glancing blows and suffered horrendous damage as several torpedoes being readied for launch exploded in her launch bays. Her crews fought to bring the damage under control, but her captain was forced to disengage from the battle. His ship's primary weapon systems were damaged beyond immediate repair and there was nothing more he or his ship could do to alter the outcome of the battle.

The hive ship moved ponderously forward, explosions bursting around it as the incoming fire from the Imperial ships came within range. Hundreds of spores vaporised in the hail of blossoming explosions, but there were always more pumped into space from the ship's churning reproductive vats to replace them.

The Dauntless cruisers Luxor and Yermetov passed the listing remains of the frigates Von Becken and Heroic Endeavour, their lance arrays spearing towards the hive ship. Turning as a single entity, a number of smaller bio-ships sped forward, hurling themselves into the path of the burning lance beams. Three exploded, torn apart by high-powered energy weapons and another was cut in two along its length. A salvo of torpedoes launched from the Cobras of Cypria squadron slammed into the hive ship, passing through an expanding cloud of fire and spores and detonated against the craft's stony carapace.

Ichor spilled from the wound, but almost as soon as the fire of the torpedoes' explosion had faded, the tear in the creature's hide began reknitting as fresh tissue formed across the beast's flank.

Suddenly a fleshy fold in the bio-ship's underside eased open and scores of finned creatures shot from its belly, trailing sinewy streams of amniotic birth fluids. A handful were blasted to atoms by fire from the Sword of Retribution as it powered forward and the Argus angled her course around the coreward flank of the hive ship, manoeuvring into a position to bring her broadside lances to bear. But none of the fleshy creatures launched from the hive ship were bound for either of the battleships of the fleet. They converged upon the Space Marine strike cruisers that escorted them.

Admiral de Corte watched the hive ship slip to the left of the viewing bay and counted down the minutes until his portside lances could fire. So far the battle was proceeding much as he had planned, though the durability of these alien craft had surprised him, despite the inquisitor's warning. There had been losses, but precise figures and exact information was slow to reach him.

'Mister Viert, status report,' he demanded impatiently.

'The Swords are out of action, Lord Admiral, and Von Becken has been completely destroyed. The Heroic Endeavour's engines have been shut down though her enginseers are attempting to relight them. Hydra squadron has lost two ships and initial reports suggest that neither will fight again without spending years in dock.'

De Corte bunched his jaw as the scale of their losses became apparent. 'I fear that we may have underestimated the cunning of these aliens,' he whispered.

'You would not be the first, admiral,' observed Kryptman.