Slaying bandits, saving maidens, and rescuing kittens. All in a day's work for any adventurer worth their salt, but once in a while, a hero's quest has world-rending consequences. Demon hordes pouring from the Abyss, a Demi-Lich awakening millennia's worth of undead, or the Gods themselves deciding the fate of the planet. 

For that you need an exception set of dice.