Quote Originally Posted by Bendraesar View Post
I guess it just makes people feel that they've accomplished something greater if they forged their idea brand new with their own two hands rather than simply innovating something that already existed.
That's a confusing statement because "innovate" means to create something that has never been done before, while the term you were probably looking for was "renovate," to make new.

As for rules on your PM querie, there are no rules for monster creation. There's a whole sack of not hugely effective guidelines [which Debbihuman slaps me around the head with fairly liberally] and beyond that it's all guess-work.

I'm all for reflavouring. If you can get Tome of Horrors, perhaps the Coffer Corpse would do...maybe ask The Vorpal Tribble to increase its HD a bunch for you [see his creature advancement thread].

If you're adding nothing else, giving Jason DR 20/something specific would probably make him about +1 CR more dangerous, simply because of the extra attacks he can get in before he's brought down. On the assumption that he were of the same CR as the party, applying this 3 times makes him damn near indestructible with DR 60 and still kind of in tune with them, at CR = party +3ish...

As another option, you could look up a critter called the Dybbuk from Fiendish Codex 1. If you strip away its death touch and spell like abilities, what you're left with is a spirit that can repeatedly repossess its corpse, creating that whole "we've finally killed him...oh, wait" feeling. Not quite Jason, but effective.