The pair spoke about the DC Comics storyline, which runs through their Animal Man and Swamp Thing titles, during Snyder's spotlight panel at San Diego Comic-Con International, at which Lemire was moderating, reports Comic Book Resources.
As hinted on the cover of Animal Man #13 - which features a decaying Hawkman - the storyline will see heroes that cannot tap into the forces known as 'The Green' and 'The Red' being corrupted by 'The Rot'.
"'Rotworld' is going to be a nightmarish look at the DCU," said Snyder.
"Imagine a world where, if you don't have a connection to the Red or the Green, you're basically going to get turned into a rot monster or die, right?" added Lemire.
"Unless you're Constantine. Somehow he survives."
The storyline was also recently revealed to be drawing in Lemire's former title Frankenstein: Agent of S.H.A.D.E., which has passed into the hands of writer Matt Kindt.
The writers promised a significant role for Frankenstein in the crossover.
'Rotworld' will launch in Animal Man and Swamp Thing #12 in August.