Falkenrath

"There are lines that even vampires do not cross, we have laws, a balance must be maintained. Falkenrath has no laws that bind him. He is a mindless plague, a waking nightmare. He has reduced himself to the singular need to feast on blood until there is none left. Then he will sit on a throne of corpses and rule a dark and empty world as the uncontested lord of nothing." -Strahd Von Zarovich

"Thick, fresh blood poured down Rawhead's throat; he gulped it greedily. The hot taste of the world. It made him feel strong and wise. The was only the first of many meals he would take; he'd gorge on anything that took his fancy and nobody would stop him, not this time. And when he was ready he'd throw those pretenders off his throne, he'd cremate them in their houses, he'd slaughter their children and wear their infants' bowels as necklaces.  This place was his." -Clive Barker, Rawhead Rex

Lore
Before he was a living plague Falkenrath came to our world more than 50,000 years ago as a planewalking vampire wizard. In his exploring he discovered that while Earth was teeming with life and had a thin but still functional magical weave it had never been exposed to vampyrism. Further still, as an outsider, Falkenrath had access to magics that dwarfed the Earths most powerful sorcerers.

With nothing to stop his spread of influence, Falkenrath gorged himself on the blood of millions, losing himself in the feast and the slaughter. After years of uncontested feeding he had become a mindless slave to his savagery; no longer able to cast spells or recall his own name, he eventually even forgot how to speak.

His downfall came decades later when Strahd Von Zarovich and Edgar Markov battled him to a stalemate and forced him through a mirror to the Demiplane of Dread. To ensure that he could never return they shattered the mirror and wandered the earth in opposite directions, scattering the pieces as they went.

Falkenrath remains trapped in Strahd's prison of Barovia where he starves on the meager supply of blood to be found compared to his usual appetite.

As documented by Fox Ashford: "The creature that lay at the heart of the miasma was obviously vampire, but starved to the point of deformation. He looked hollow; as if in his hunger he had eaten himself from the inside out. His skin had calcified and his eyes long since withered to dust. All that was left of his face was a mouth full of knives, and a hole in his head where his nose used to be, but don't be fooled; that nose was the control center of the whole hivemind. A nose for smelling blood."