Help! I need a campaign boss char sheet

[SalSar_Thiran]

So my RL campaign is winding down, and the time for the final fight has come.
Problem: I fail at designing good encounters and this one is supposed to last.
Solution: Ask the awesome people here at Giantitp.com for help.

Requirments: Karrai is a 4000 year old vampire.
May have cohorts up to level 10, and cr 5 monsters of my own design.
Retreat is not an option for either side for any reason.
Party is 8 people: human Paladin, Fighter(grappler), gnome wisard, human wizard(necro), human ranger, Dwarf dwarven defender, gnome bard, human barbarian. Entire party is level 13. (these are long time players and are specced to high he**)
Party also has a 15 hd half-fiend ally who has yet to be able to do anything in combat.
If possible I would like this by thursday but if more time is needed I can gladly put the session off.

Thank you very much for any help you can give.

[Legoman]

A CR 15 vampire (Say, with 7 class levels... Wizard maybe?) should be fine for this encounter. The trick is going to be not making this a standard tank-and-spank, but instead making it a harrowing encounter through the use of environment and unforseen special abilities.

Consider the following:

I'm running my players through a 'training session' that's really their final exam for this shadowy-type guild.

One of the intermediate encounters is two level 3 Warforged, massive Sheilds, heavy armor, boots of Jumping. That's it.

However, the environment is what makes it interesting - the room is made of 9 10x10 platforms, that all move randomly up and down independently of each other. Occasionally, steam bursts from the floor of one of the platforms, and deals 1d6 fire damage.

As if that wasn't enough, so the caster's can't fly around and do mayhem, there's whirring blades and hooks and the like that occupy the space near the top of the room - any higher than 10' off the platforms at the highest points, and you have to make Reflex Saves for each square/round you're up there, or get slashed up.

How are they going to beat it? I don't know, I expect a lot of bull-rushing and such... but the warforged are basically just going to push them about so they fall off the platforms and have to take AoO's climbing back up.

Try something like that.