Campaign Help: Vampire Coffins, Creature Melding

[Fellwarre]

Okay, I had an original post that I was going to do, then I realized it was totally TL:DR. I wouldn't have even read it, so I need to get to the nitty-gritty of the question.

I'm willing to buy whatever books I need to, so if someone doesn't want to post copyrighted rule information and just tell me what book to get, that's perfectly fine with me.

First: What happens if a vampire's coffin is destroyed, but as a GM I don't want the Vampire to die? I have a vamp bad guy and I'm thinking he's wearing a magic item with a contingency spell on it that says when he's dropped below a certain HP, he'll Timestop, Teleport, and Fireball (to destroy his current surroundings.) I want the players to see the burnt husk of his coffin, but I want my vamp to be a recurring character. Would it be within the rules to say he can perform some rite to get a new coffin?

Second: I've spoken to a player about a character... class? Feature? A character or monster that's able to 'meld' two characters together, for instance, to give a human T-Rex arms, a duck's bill, and ostrich wings. You know, to make a completely useless human. Does anyone know what we're talking about and where I would find the rules for this?

Thanks in advance for the help, all! =D

[Garagos]

I myself run a campaign where most of the PCs are vampires. I allow them to "attune" themselves to new coffins for any reason they like, but they can only ever have one at a time. I just make them spend a full 24 hours resting in the coffin without leaving it. Once that's completed that is the new coffin they must get to if they're dropped below 0 HP and turn to gaseous form.