Since I might as well give people some idea of what I intend-my vampires will be linked to a plague. The Red Death-if you're familiar with Edgar Allen Poe, I think you'll know how this goes. How the vampires rose to power. If there is one consistent theme in medieval power structures, it's that the vast majority of humanity experienced great limitations on their freedoms and rights while the nobles enjoyed a far larger amount of freedom in the form of wealth and influence-often stolen, one way or another, from aforementioned vast majority. 

And it was so rarely the nobles who suffered from the ills of plague and war, of starvation and cold weather. They were safe in their castles...

Such was the case in this land. Working name is Carpathia, as a reference. Might keep it. Carpathia has always suffered from outbreaks of the Red Death, from monsters plaguing dark forests, and from restless dead. Vampires too, stalked in the darkness. But their ascension to true power is recent-and built on the crimes of the nobility. There came a time when the Red Death did not just scar the land, but [i]burned[/i] through it. Many died, mostly of the lower classes. Dying alone in their hovels, or in great, choking cities. More died every day. Drowning in their own blood. 

All while the nobles waited for the plague to end. All while they barricaded themselves away. Safe behind their walls and guards. 

Safe from the plague, but not from those they left to die. The Red Death kills nearly all it touches-but those who survive, who somehow fight through the disease...are changed. They rise. Stronger then ever. Their eyes burn with necromantic power, and their canines lengthen. Power of a darker sort flows through their veins.

And they remembered, they remembered who had left them and theirs to die.

What followed were days of fear, for those nobles, and nights of blood and terror. Swiftly, the castles and homes of these nobles were ravaged by those they had thought doomed to die. Noble necks were ripped open. Guards slaughtered. 

And it fell to these new vampires to rule this suffering nation.

Irony of ironies, their rule, despite their terrifying abilities, despite the dead they raise as soldiers, despite all the black magic they can bring to bear, has turned out to be far more just then the rule of the church and the nobility. 

This is all condensed, but you get the idea I hope.