Now, here's a thought.
Spoilered so the players can read it, but not the DM for now
[sblock]Sunbeam is a great spell against vampires - it destroys them.
... on a failed Reflex save.
The issue there, of course, is that Kurin likely has an insanely high Reflex save.
So we need a way to lower the save.
Depending on interpretation of certain key sentences, when someone is bound, they either a/ can't make a Reflex save, or b/ make a Reflex save with an effective Dex of 0 (-5 modifier instead of their normal +whatever).
A set of Iron Bands of Bilarro - bind an opponent, ranged touch attack, no save - costs 26k. It wouldn't hold a vampire long - gaseous form would get him out - but with the right readied actions, there wouldn't be a chance for him to escape...[/sblock]
-Hyp.