The story of Spawn: Armageddon is a simple one: Heaven and Hell are using Earth as their battleground, and if Spawn doesn't put a stop to it the world will end.
The game opens with Spawn sitting on the rooftop of a church having a flashback of the horrors of his death by the hands of Jason Wynn. Suddenly, an enormous green beam comes down from the sky and hits the city, knocking Spawn from his perch. Spawn quickly learns that the beam was the signal for the beginning of Armageddon, the war between Heaven and Hell. He needs to tear through streets filled with battling angels and demons (while neither side would mind claiming his head) in order to put a stop the the war and save Earth. Spawn's travels take him through grungy parts of the city, a city park, Hell, and even Outer Space. Some familiar faces such as The Violator, Mammon, and Malebolgia make appearances.