A tiny spark landed in the gaseous mist, causing a local temperature increase.
The gas in the Gaseous Zone was originally very "pure"; intense oxidation-reduction reactions simply wouldn't occur.
But as the population of metallic life forms grew, their metabolic byproducts saturated the Gaseous Zone, making the gas here more "complex."
To say nothing of the gaseous life forms scattered about, whose very bodies were complex and active gaseous compounds.
And so, as the spark passed through the cloud layer, everything around it ignited.
The flaming moth tore a bright line of fire through the air. This line grew thicker and thicker, eventually erupting into a pillar of fire that shot toward the heavens.
Scorching tongues of fire flickered, devouring all the surrounding gas.
