When Post-Apocalyptic Monsters Attack : Black Mutant Radiation Eating Fungus

Apparently this stuff has adapted to a wide range of conditions here on Earth, including a reserve state that must come in handy every couple of millennia when dangerous high radiation levels cause it to become a melanin-loaded coal black pus-oozing troublemaker eroding everything in it's path. There's a really ironic joke in there somewhere but I ain't touching it.