so what...

[hivedragon]

(in eberron)
if King Kaius was found out to be a vampire?

in Karrnath it's considered patriotic to join the army twice
(the second time as an undead)
the main religion is devoted to ending natural death

would it really be a big deal if people found out his secret?

[Cog]

Well, vampires are a particular kind of undead. They aren't created after somebody's lived their life once; they're transformed. They don't subsist solely off negative energy, but need to feed on the living. They're possibly beholden to whichever master sired them.

Alternatively, this is Eberron, where a lot of blanks are left for you to fill in. There might be more he's hiding than just that he's a vampire. Perhaps he truly is still beholden to his mistress?

Of course, it's probably the other secret that he's primarily hiding. The vampire thing just might be a clue to his identity and so he's covering that incidentally.

[supermonkeyjoe]

I think the problem with Kaius being outed as a vampire is not public acceptance but the attitude of his Warlords. From my understanding most of Karrnath's warlords would use any excuse to usurp Kaius from the throne as they despise his peace-mongering ways.