As with the other thread I started, this is for advancing the main bad guy from Expedition to Castle Ravenloft, as it is designed for characters levels 6-10, and my 3 players are entering the adventure at 9th/10th level (10th level Druid, 9th level Fighter, and a changeling Rogue 5/Warlock 4).
In the module as designed, the PC's enter the adventure at 6th level, and over the course of the extended quest, level to 10th level, and drop Strahd's CR from 15 to 12 by stripping him of his Fane Signs. Strahd is a 10th level Wizard with 70 HP's.
As my PC's are basically 4 levels above where they should be, but because they are only a group of 3, rather than 4 (though with a tough animal companion), I was thinking to add 3 or 4 levels to Strahd. The easy answer would be to add 3 levels of Wizard, though it would do nothing but grant him 3 casting levels (and 7th level spells), an average of 19.5 HP's, and one feat from HD levels.
Another interesting option would be to give him the 3 level PrC Master Vampire from Libris Mortis. It only grants 2 caster levels, but might give him some nice bonuses. I've got a question about the "More Spawn" class ability. It says it increases the HD of spawn that the vampire can have under control to twice his HD + Cha mod (example, 10HD vamp with 18 Cha can have 28 HD of vamp spawn controlled). But the vampire template doesn't limit the HD of the spawn under control of a top vampire; it only limits the number of individuals the vampire may control as equal to twice the top vampire's HD.
At any given time a vampire may have enslaved spawn totaling no more than twice its own Hit Dice
So, which is it?
If I do go the Master Vampire route, I may give him the 4th level boost, meaning he still gets 3 extra caster levels.
I'll probably give him the Improved Toughness feat at his 12th HD, thus helping shore up that weakness.
Thoughts? Alternate suggestions?