Re: So the King is a Vampire
Vampire king? That sucks.
It's all very relative, as everybody has pointed out. And aside from needing to read "Knights of Dark Reknown" now (once I'm done with "Echoes of the Great Song"), I'll add a quick thought.
The thing about vampirism is that in many mythos, it locks the victim into a permanent nocturnal state. Combine that with extravagently long life, amazing supernatural power, and the need to feed on human prey, and you have an excellent formula for a villain. Over the course of a lifetime, most people become mere amplifications of what their nature draws them toward. Silly people become sillier, the wise become wiser, etc. We move toward an extreme unless or until something cataclysmic happens.
And so I reason that most vampires are evil based off of an eternity of darkness, predatory feeding, and the betrayals involved with many fantastic "vampiric courts", such as those seen in Vampire: the Masquerade.
Other fantasies argue a much more unnatural sort of evil that draws out of the vampire-- Buffy: the Vampire Slayer suggests they lack a soul and thus become selfish, murdering, callous monsters. David Gemmell also wrote "Morningstar," where a vampire does not feed on blood but rather on innocence, as true a monster as any. But I always preferred my vampires moving toward evil at their own pace, slowly losing their humanity as centuries slip past.
You need to decide on what kind of stake-holster your king is-- the soulless or the sophisticated.
Also, what kind of Champions of Good are these? A Paladin who fights for the Lady of the Light is going to want a strong moral agent on the throne (not that strong moral agents can't be frightening in power. . . .). If they're headed up by a world-weary general who knows that politics are a matter of choosing between bad and worse, then it will be more a matter of policy than biology.
Personally, I like the idea of a dark ruler. I'll have to look that Eberron stuff up. But if nothing else, this is the kind of discussion I'd rather seen played out in a game between the PCs than anything. Watching the friction could be interesting.