Theo quickly shut and sealed the door before the mist had a chance to make it to him. He wanted to enjoy the show but Hermione warned him the particular strain dragon pox was incredibly potent and there was a chance of exposure. The poison used to the petrify the body would continue to tighten the muscles into very strong walls, in a bit of a twist, Hermione ensured it would keep the victim alive until his body could no longer remain together. Thoros loved to torture and Theo felt it was only right to give a little back to the man.