Valakut, the Molten Pinnacle

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

Topiary Stomper

Vigilance (Attacking doesn't cause this creature to tap.)
When this creature enters, search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
This creature can't attack or block unless you control seven or more lands.

Sutina, Speaker of the Tajuru

When Sutina enters, search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Whenever Sutina attacks, you may return a land you control to its owner's hand. When you do, put a +1/+1 counter on target creature.

Fecund Greenshell

Reach
As long as you control ten or more lands, creatures you control get +2/+2.
Whenever this creature or another creature you control with toughness greater than its power enters, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped. Otherwise, put it into your hand.

Gladiolus Amicitia

When Gladiolus Amicitia enters, search your library for a land card, put it onto the battlefield tapped, then shuffle.
Landfall — Whenever a land you control enters, another target creature you control gets +2/+2 and gains trample until end of turn.

Mountain

Arboreal Grazer

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