Apocalyptic Vampires travel from world to world through interdimensional cracks, such as the ones in The Nexus on Earth, and then set up shop. At first they work in the shadows, manipulating things and getting thralls into places of authority. Then they do things like start nuclear wars, bio wars, or anything that'll throw the world into complete and total chaos. Nuclear winter is good because then they can go outdoors more. Then they come out of the shadows and rule.
Apocalyptic Vampires feed on the souls of their victims, draining them of will until they become puppets. (They can eat but don't need to; they have some good recipes involving liver, intestine-wrapped sausages, blood pudding, steak tar-tar, blood wine, etc.) Their victims begin to turn a little twitchy, slowly turning psychotic and decomposing zombie style, so they have a short shelf life.
After achieving an apocalypse, they keep human cattle in pens and a rely on thralls to keep order. Some of the Vampires have formed factions; their thralls will take on a certain style of dress to show their allegiance. Two factions in particular are the Clowns and the Cheerleaders. Picture a fat, hairy, putrefying man in a cheerleader's outfit using a whip to drive human cattle. Or a group of smiling clowns having some fun with a person before going through with the slaughter to feed their master.
There is a resistance: a group of humans trying to take back their own world. The leader, a charismatic man in his 30's, has acquired a sword which is capable of defending its bearer from the mind control of the vampires and is especially good at severing heads from shoulders.