The Monstrous Misadventures of Rusty & Co.

[The Glyphstone]

Hmm, wouldn't garlic count as a standard vampiric weakness?

Possibility: instead of taking away their standard weaknesses, the python gave them new weaknesses.

Possibility: the gorgon-made pizza is in some way infused with the gorgon's stoning breath power.

Think more meta. No 'vampires' these days are vulnerable to garlic, it's the new 'mainstream' for them to be unaffected. Thus, to be truly hipster and avant-guarde, they went back to classical roots for a weakness no one has anymore. Oops.