In void war, structure was everything. In the open void, a fleet’s defence hung entirely on its overlapping formation. Every warship of the Legiones Astartes was ferociously, almost comically, over-armed – built to subdue the galactic empires of xenos, each was the equal of an entire world’s sub-warp defences, capable of dishing out phen¬omenal rounds of atmosphere-shredding punishment from long range. Putting such vessels into geometric patterns in which every single ship guarded the flanks of another produced an exponential multiplier effect, and thus Crusade war-fleets slid through the void like glittering predator packs, giving an enemy no unwatched facets and no open sectors. To break a settled Imperial fleet formation was a daunting task, and every shipmaster in every battlegroup knew the importance of maintaining the armour of numbers.

But this was not the open void. The Alaxxes tunnels prevented the most flamboyant outflanking figures, and so what was left was a test of speed and close-range manoeuvring, something that the VI believed gave them the advantage. Though they couldn’t match the XX Legion’s patient accumulation of territorial advantage, they could outdo them in daring.

So the Space Wolves outriders hurtled into contact with a kind of feral abandon, rolling away from incoming flak-battery fire, their lances burning like stars. The Alpha Legion vanguard fell back, maintaining their interlocked position, soaking up the first assaults.

It took only seconds for the capital ships to engage. Making use of the narrow channels cleared by the strike cruisers’ runs, Ragnarok launched a massed salvo of torpedoes, backed up by lance-fire from its escorts and tightly packed broadsides from its own macrocannons.

That hurt the Alpha Legion ships. The volume of impacts, launched all at once, smashed frontal void-coverage and sheered adamantium buttresses. Gunn had ordered every commander to run primary weapons grids at overcapacity, running the risk of system overload but giving a savage punch to the opening exchanges. Two hurtling Wolves destroyers were lost in catastrophic explosions as their power-containment systems failed, but the resulting maelstrom compensated for their loss – half a dozen Alpha Legion ships were crippled or destroyed in the blaze, including a Dominus-class monster with the ident Gamma Mu.

That, though, was not the primary purpose of the attack. Hangar doors on every warship hissed open, bleeding oxygen into the void in plumes. Waves of boarding torpedoes burst from the delivery tubes, clustering and twisting before locking on to strike coordinates. Secondary wings of gunships launched while the mother ships were still at attack speed, shooting off on pre-planned assault vectors as the lateral batteries opened up behind them.

Lord Gunn had made his move, committing the fleet to close-range assault, and it lit the gas tunnel walls with sunbursts of thruster backwash. Powering towards the hulking monsters ahead, the salvoes of tiny assault craft screamed towards their targets, taking the slender hopes of their Legion with them.