Cleansing Wildfire

Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.
Draw a card.

Mind Bend

Change the text of target permanent by replacing all instances of one color word with another or one basic land type with another. (For example, you may change "nonblack creature" to "nongreen creature" or "forestwalk" to "islandwalk." This effect lasts indefinitely.)

Island

Quag Vampires

Multikicker {1}{B} (You may pay an additional {1}{B} any number of times as you cast this spell.)
Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Quag Vampires enters with a +1/+1 counter on it for each time it was kicked.

Mountain

Plague Beetle

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)

Ghost Quarter

{T}: Add {C}.
{T}, Sacrifice Ghost Quarter: Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Lord of Atlantis

Other Merfolk get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Counterspell

Sea's Claim

Enchant land (Target a land as you cast this. This card enters attached to that land.)
Enchanted land is an Island.

Blood Moon

Contaminated Ground

Enchant land
Enchanted land is a Swamp.
Whenever enchanted land becomes tapped, its controller loses 2 life.

Anger of the Gods

Anger of the Gods deals 3 damage to each creature. If a creature dealt damage this way would die this turn, exile it instead.

Swamp

Evil Presence

Stone Rain

Roiling Terrain

Destroy target land, then Roiling Terrain deals damage to that land's controller equal to the number of land cards in that player's graveyard.

Rishadan Dockhand

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
{1}, {T}: Tap target land.

Goblin Mountaineer

Mountainwalk (This creature can't be blocked as long as defending player controls a Mountain.)

Infernal Reckoning

Exile target colorless creature. You gain life equal to its power.

Spreading Seas

Enchant land
When Spreading Seas enters, draw a card.
Enchanted land is an Island.

Molten Rain

Destroy target land. If that land was nonbasic, Molten Rain deals 2 damage to the land's controller.