The twisted corrupting of the area of man. It is unknown if The Burn is contained to the planet, or if the whole dimension of rage and destruction is spilling into ours.
Little is known about hell, but what can be seen from The Burn, nothing is immune to it's corruption. Lands blister, air becomes rancid and poisonous, the lucky creatures and plants die. The ones that don't die will be found by demons before their deaths, having their souls eaten while still alive. The still living humans and animals, undead to some, live in a state of eternal pain of the tearing of their soul.
The only things that can survive once The Burn is completed will be the demons, minions of its destruction. No trace of anything living will remain when Hell has overtaken this little patch of order. Once The Burn is done, the last remnants of humanity will have no chance of survival, as no area that can feed a sufficient population will survive.
The only thing left then will the near mindless masses of zombies, till those too are devoured.