Tundra Kavu

{T}: Target land becomes a Plains or an Island until end of turn.

Celestial Dawn

Lands you control are Plains.
Nonland permanents you control are white. The same is true for spells you control and nonland cards you own that aren't on the battlefield.
You may spend white mana as though it were mana of any color. You may spend other mana only as though it were colorless mana.

Aysen Highway

White creatures have plainswalk. (They can't be blocked as long as defending player controls a Plains.)

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Unstable Frontier

{T}: Add {C}.
{T}: Target land you control becomes the basic land type of your choice until end of turn.

Mystic Compass

{1}, {T}: Target land becomes the basic land type of your choice until end of turn.

Boggart Arsonists

Plainswalk (This creature can't be blocked as long as defending player controls a Plains.)
{2}{R}, Sacrifice this creature: Destroy target Scarecrow or Plains.

Graceful Antelope

Plainswalk (This creature can't be blocked as long as defending player controls a Plains.)
Whenever this creature deals combat damage to a player, you may have target land become a Plains until this creature leaves the battlefield.

Plains

Mountain

Righteous Avengers

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

Blood Moon

Lush Growth

Enchant land
Enchanted land is a Mountain, Forest, and Plains.

Zodiac Rooster

Conversion

At the beginning of your upkeep, sacrifice this enchantment unless you pay {W}{W}.
All Mountains are Plains.

Nature's Lore

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Forest

Magus of the Moon

Jetmir, Nexus of Revels

Creatures you control get +1/+0 and have vigilance as long as you control three or more creatures.
Creatures you control also get +1/+0 and have trample as long as you control six or more creatures.
Creatures you control also get +1/+0 and have double strike as long as you control nine or more creatures.

Circuitous Route

Search your library for up to two basic land cards and/or Gate cards, put them onto the battlefield tapped, then shuffle.

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.