Thick, poisonous vapour swirled through its corridors, growing thicker the higher up the ship’s decks one went. At the very heights of its rotten command spires, the gas displaced the air, and would kill a mortal man in seconds. The cowed tribes who made up the ship’s mortal contingent were confined to the lower decks, where the air approached breathable and the fog was confined to ceilings of the highest halls, snaked and coiled among the corroded ducts. Even so they lived terrible, shortened lives, their lungs rotting from the moment of their first breath.

To the daemon primarch Mortarion, the air was invigorating. He strode through its comforting billows. His robe sent it into a storm of complicated curls where three-lobed sigils and grinning skulls might be seen, though only for a moment. In the high levels he walked, the mist was liquid thick and hid the sides of the corridors. Glinting droplets made up the clouds, condensing on metal and flesh, and moisture beaded the primarch’s clothes. Other parts of the Endurance were sweltering as equatorial swamps, but the heights were chill as mountaintops, and here daemonkin, immune to the effects of the toxic air, took the place of wretched humans as crew. The air aside, the machinery of the vessel in the heights required a certain touch. No mortal effort could ensure its smooth running.

Coiled, organic tubing took the place of metal pipes. Taut nerves replaced wiring. Rotting brain matter stood in place of circuitry nexuses, and daemons trapped in warded pots did the work of cogitators. A thick plaque of pulsing flesh covered over the walls and made the floor soft underfoot. Where it had not been subsumed, the steel and iron of ancient Imperial work was flaked with corrosion. Blackened plastek peeled from wiring. Everywhere was a state of decay.

The fleshy parts of the Endurance teemed with disease that broke it down and digested it as quickly as it grew. Great patches of it were black with putrescence. Crops of livid cysts throbbed on the walls, trickling oil where they had burst. There were rooms where the flesh had died. There maggots fell as rain, and flies clogged the workings. Whole decks had been overtaken by foetid jungles. Others were thick with slime where unnatural ecosystems had succumbed to virulent plagues, for the interior of the Endurance was a small part of Grandfather Nurgle’s Garden, dug up and transplanted into the fertile ground of the mortal world.

It was a vital decay. The ship still functioned. It still moved through space as it had been made to. It quivered as its ancient engine stacks pushed it vigorously free of the Macragge System.

Mortarion’s personal domain differed in form to the chaotic machine-life of the rest of his ship. He came to a door covered with throbbing, vein-like ivy. A pass of his cadaverous hand, and the door opened for him, sending the choking fog into a swirling dance.