The moon of Umbriel swung across the sunward edge of Uranus as the fourth day of battle began. Armoured hab-domes dotted its craters, and tethered gun bastions hung in its airless skies. A quartet of assault carriers detached from the Daughter of Woe and boosted towards the emerging moon. Layered in armour and void shields, their hulls groaned with troops suckled from the guts of the hulk. A pair of battle cruisers fell in beside the quartet of carriers and the IV Legion strike cruiser Aesculus dropped into the lead of the formation.

A group of six warships lay across their path. Smaller than the traitor cruisers and assault carriers, they were Legion ships, four of the Imperial Fists and two of the Blood Angels. Their troop complements had been stripped to garrison Terra, but their commanders were still some of the finest void warriors in the Imperium, their crews trained and drilled to Legion standards.

They began to fire, moving and rolling in the void as they closed with the oncoming enemy. Torpedoes surged from the prows of the attackers. Squadrons launched from the defenders’ ships to tear the warheads from the void. Lance beams danced over the assault group’s shields.

The six loyalist craft accelerated, their guns singling out an assault barque. The ship listed, its belly crawling with flame, skeins of oily energy stuttering around its hull as its shields failed to light. In its holds, a hundred thousand soldiers taken from the Grey Worlds of the Kayuas Belt became ash as plasma vented from cracked conduits.

Fire criss-crossed the void as Umbriel’s defence turrets targeted the oncoming torpedoes. Explosions ringed the small moon. Then the nova shell struck it. Fired from a bombardment cruiser far out of the battle sphere, it had been timed to strike just at this moment. Primed with a haywire generator and thousands of scrap-signal initiators, it burst on Umbriel’s surface. Clouds of distorting energy and ghost auspex signals fogged the defence sensors just as they locked on to incoming torpedoes. Graviton and haywire warheads struck Umbriel moments later. Crushing gravity fields yanked the moon’s tethered bastions out of alignment and cracked the shells of surface habitats.

The strike was not decisive, but it made Umbriel’s defences blink – and that was enough. A stutter in the deluge of fire from the guns, a split-second’s pause, and the assault carriers began to shed breaching pods like seeds from ripe corn-heads. Their warship escorts came about to meet the six defenders head-on.

Gunships cut through the void around growing thunderheads of burning gas. Their targets were the gun platforms tethered to the moon. Those craft that struck true poured troops into the guts of the moon’s bastions. Corridors lit with gunfire. One bastion detonated its magazines, and the fire-scattered night was dotted with a brief new star.