Tsunami

Boiling Seas

Yidris, Maelstrom Wielder

Trample
Whenever Yidris, Maelstrom Wielder deals combat damage to a player, as you cast spells from your hand this turn, they gain cascade. (When you cast the spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Return of the Nightstalkers

Return all Nightstalker permanent cards from your graveyard to the battlefield. Then destroy all Swamps you control.

Hellfire

Destroy all nonblack creatures. Hellfire deals X plus 3 damage to you, where X is the number of creatures that died this way.

Acid Rain

Nature's Ruin

Boil

Reign of Terror

Destroy all green creatures or all white creatures. They can't be regenerated. You lose 2 life for each creature that died this way.