The Great Fontaine Flood

(You may cast a legendary instant only if you control a legendary creature or planeswalker.)
Destroy all creatures. Whenever a creature
enters the battlefield from your graveyard this
turn, draw a card.
And so the Primordial Sea rose, washing across all of Fontaine, and fulfilled the prophecy. But thanks to the sacrifice of Focalors, the Fontainians were saved.