Valakut, the Molten Pinnacle

Valakut, the Molten Pinnacle enters tapped.
Whenever a Mountain you control enters, if you control at least five other Mountains, you may have Valakut, the Molten Pinnacle deal 3 damage to any target.
{T}: Add {R}.

Cinder Glade

({T}: Add {R} or {G}.)
Cinder Glade enters tapped unless you control two or more basic lands.

Scapeshift

Sacrifice any number of lands. Search your library for up to that many land cards, put them onto the battlefield tapped, then shuffle.

Sakura-Tribe Elder

Sacrifice Sakura-Tribe Elder: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Forest

Primeval Titan

Trample
Whenever Primeval Titan enters or attacks, you may search your library for up to two land cards, put them onto the battlefield tapped, then shuffle.

Wrenn and Six

+1: Return up to one target land card from your graveyard to your hand.
−1: Wrenn and Six deals 1 damage to any target.
−7: You get an emblem with "Instant and sorcery cards in your graveyard have retrace." (You may cast instant and sorcery cards from your graveyard by discarding a land card in addition to paying their other costs.)

Mountain

Summoner's Pact

Search your library for a green creature card, reveal it, put it into your hand, then shuffle.
At the beginning of your next upkeep, pay {2}{G}{G}. If you don't, you lose the game.

Search for Tomorrow

Search your library for a basic land card, put it onto the battlefield, then shuffle.
Suspend 2—{G} (Rather than cast this card from your hand, you may pay {G} and exile it with two time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)

Dryad of the Ilysian Grove

You may play an additional land on each of your turns.
Lands you control are every basic land type in addition to their other types.

Taiga

Stomping Ground

({T}: Add {R} or {G}.)
As Stomping Ground enters, you may pay 2 life. If you don't, it enters tapped.

Harrow

As an additional cost to cast this spell, sacrifice a land.
Search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Arboreal Grazer

Reach
When Arboreal Grazer enters, you may put a land card from your hand onto the battlefield tapped.