Warhammer 50k: Engulfed by the flames

The latest entry in my 'Warhammer 50k' fan-project, with the aim to get a glimpse of what might transpire in the grim-dark universe 10000 years into the future. Follow the series here: https://www.artstation.com/huhwowproductions/albums/13707272
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It is the 51st millenium, and Holy Terra has fallen.
As several Orkish WAAAGHS! and Tyranid hivefleets wreak havoc the likes the galaxy has never seen, and the new Chaos warmaster gathers forces for a final unholy crusade upon the enemies of the Dark Gods, things surely look more grim than ever.
These are the tales of those times...
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After a millenia-long absence primarch Vulkan finally returns to the Imperium. But all is far from well.
Having lost his powers as a Perpetual sometime during his journeys Vulkan is now dying. Gripped by an insidious affliction known as the 'smoulderot' the primarch is slowly, but surely, burning to cinders from within.
To make matters even more dire he finds himself returning to an Imperium much different than the one he left. And an Imperium on the very brink of annihilation none the less.
And perhaps the worst of all; most of his gene-sons within the Salamanders legion have done the unthinkable and defected to the Ruinous Powers, dragging several successor chapters with them into corruption as well.
So as Vulkan joins the effort in keeping the failing Imperium from total collapse he must also unravel the truth behind his own legions ultimate betrayal. It is a race against time, a race the primarch must finish before being claimed by his final death.