I looked at six parts of Justus Whitmore; the corrupted valley fire would have killed him already. If I was burning under such fire, I would have died within a minute.
As I had said, it is no common fire but fire from someone who is part of a coven. They are the most powerful Grimms that rule their whole race, and even to kill the weakest of them, the whole pyramid council would have to fight against them.
From what I could see, the only reason he was able to survive was because of the artifact. Even now, he is divided into six parts; there are tens of elastic strings connected to all of his six cut body parts of his.
Such artifacts are extremly rare, considering how they get suppressed the closer they get to the limit of the world.