Between rain of fire and immolation our quanta denial strategy with devourers is rendered near useless. Since Darkness has very little CC I'd expect some sort of creature rush from Fire. Golems and Phoenix are problematic unless you've got something like antimatter, freeze, basilisk blood or reverse time to deal with them. Their graboid rainbow with Rage Pots is one of the best decks in the entire war.
Fire is likely to bring 2-4 deflag so we're better off either bringing no permanents or going overkill and bringing multiple copies. I think an Entropy/Darkness combo or our own graboid rainbow is our best bet against Fire.
Some of Fire's best decks in the last war:
5f0 5f0 5f0 5f0 5f0 5f0 5f0 5f6 5f9 5f9 5f9 5f9 5f9 5f9 61o 61o 61o 61o 61o 61o 622 622 622 622 7ds 7ds 7ds 7ds 7ds 7ds
4vh 4vj 4vj 4vj 4vj 4vj 4vj 52q 590 590 590 590 5c1 5f0 5f0 5f0 5f0 5f0 5f0 5f3 5f3 5f6 5f6 5f6 5fb 5fb 5fb 5fb 5og 5og
5f0 5f0 5f0 5f0 5f0 5f0 5f0 5f3 5f3 5f3 5f3 5f6 5f6 5f7 5f7 61o 61o 61o 61o 61o 61o 61t 61t 61t 61t 61t 621 621 621 621
52o 52o 52o 52o 52o 52o 52q 52q 5f0 5f0 5f0 5f0 5f0 5f0 5f0 5f0 5f0 5f0 5f4 5f4 5f4 5f4 5f4 5f6 5f6 5f6 5fb 5fb 5fb 5fb