Heaven
{X}{G}Instant
Heaven deals X damage to each creature with flying.

Instant // Sorcery
Instant
Heaven deals X damage to each creature with flying.
Sorcery
Aftermath (Cast this spell only from your graveyard. Then exile it.)
Earth deals X damage to each creature without flying.
This card has a static ability that applies continuously as long as it's on the battlefield. There's no trigger or activation — the effect just exists. Removing the permanent is the only way to stop it.