The Earth of Upsilon is very similar to our own with one important exception: it is a version of Earth where myth and legend are little different than actual history. Vampires, demons, witches and all manner of supernatural beings live in the shadows of humanity.
It is an alternate history where Illuminati groups composed of the undead have guided the development of human civilization for their own ends for millennia. Unfortunately for the world of Earth Upsilon it is also a history with an ending.
In their hubris, the vampires guided civilization toward the massive population of the early Twenty-first Century. In a world of seven billion people the several thousand vampires could hunt with impunity. With the rise of technology, their deathlessness has made them akin to gods.
But their arrogance also made them careless. In the end, a cabal of necromancers unleashed the final plague upon the Earth. A plague among the humans which would ensure the ultimate destruction of everything the vampires had built.
It was the zombie apocalypse.