I lost a run the other day to a series of events, one of which included me (in-game) finding and eating enough psychedelic fungus to trigger a shift in reality, which transmuted all smoke in the universe and any created thereafter, into acid. Like carbolic acid, not the fun drugsy kind.

Acid, naturally, eats through all creatures and materials in the game world, including many things you'd consider otherwise invulnerable, until it evaporates - into flammable gas.

Therefore any time an object or material caught fire (which is often, with or without player interference), it would quickly consume anything below it for several meters while feeding itself with flammable gas and spreading to any new flammable materials it uncovered.

The world very quickly became a very large mess.