The Commander by Waspeater
Disclaimer; I don't own any of the Warhammer/WH 40k elements in this, Games Workshop do, along with a fair-sized chunk of my soul.
A bit of fluff I did back in 2008 for my Blood Angels renegade successors - the Blood Dragons. They use iconography from the WFB vampires of the same name, have given themselves over to Slaanesh and their signature mutations make them look like the Reaper strain from Blade 2.
BTW it's meant to be over-the-top and ridiculously melodramatic - it's 40k.
Feedback please, even if it's negative, it's the only way I'll learn.
The once-man who still styled himself 'Commander' laughed, bellowed with laughter at the pious defiance of his captive. The sound alone would have been horrific enough to inspire night-terrors even without the massive, distended gape of his freakishly articulated jaws. He leaned in close to the Imperial noble and knew a moment's fleeting respect for the man, weak in so many ways, yet with the strength of character not to shrink back in the face of his beautiful monstrosity. He would die swiftly, by the blade, as was fitting to his station.
"You call me unnatural, your grace?" he enquired, "for feeding on the blood of men?"
The commander straightened and began to pace about the chamber with his hands folded behind his back. "Nothing could be more natural, in point of fact. A multitude of creatures on worlds unnumbered do precisely the same. Zouvan Dusk-cats, those little Jopalli lizards the locals call 'Zang', the Strix birds of Rinn's world ..." he paused to look directly at the Duke in his torn and befouled silken finery, "I wonder if they have learned to sup orkish blood? Even many species of ancient Terran lineage such as leeches, lampreys and all manner of insects feed directly on the stuff of life itself."
One of the dukes daughters hissed unexpectedly - "Vampire! Diabolus extremis!"
The dark, deep pools of the renegade's eyes flicked over her. He grinned. Such spirit! Such pleasure would be had from the breaking of her.
"One of the many interesting facts we have recovered from the data stacks of this vessel is that the vampire bat of myth is not a myth after all. They flew on antique Terra, back when that worthless ball of rock still boasted oceans, jungles even. There still is one vampire on Terra of course; that mouldering corpse, your ... God-Emperor. He feeds on the life-force of ten thousand men every single day. Women and children too, you understand? Just like me!" He chuckled at merely human volume, span on his heel and advanced on the shackled huddle, his voice rising to stentorian declamation."Yet I feed by way of biology! The delectable ichor flows like fine wine down my gullet as the soul-energies permeate me. Your zombie god requires a machine, machinery covering vast acreage, machinery that rises like a mountain or a hive city! Machinery that anywhere else in your maggot ridden Imperium would be foulest magick and blasphemy!"
Now he was once again leant down to the duke, but this time the weakling could not meet the gaze that bore into him, could not help but try to cower away from the hatred and vitriol that spat from that terrible maw with it's needle teeth.
"YOU CALL ME UNNATURAL?"
He drank in the scent of their terror and silently offered up a triple prayer of thanks to the Prince of Chaos. He thanked Slaanesh twice for his salvation. Firstly, salvation from the rotting inhabitant of the so-called golden throne, who had let holy Sanguinus die in agony, by whose decree he had been denied any true pleasure. Secondly, salvation from becoming the unthinking barbarian slave of another throne, one of skulls. The last stanza of his trionic supplication was in gratitude for the pleasure he was about to receive and the pain he was about to mete out.