[Fiberfar]

Is the master the same as The Maker?
Or is it the undead priest Sodalis

If it is the second, I suggest you use as Xandax says, all the buffs you can find if you are a fighter class. If you are a spellcaster, get hold of a Undeath to death scroll and use it. Even better is if you use a sunburst spell (which instantly destroys Vampires if they fail their reflex save).

A Paladin/Champion of Torm should use their abillity to smite evil. If it is Sodalis, he will most likely use spells that damage your player when you make melee attacks. So if you can, either use a bow or wait untill the spell duration expires.