Mountain

Experiment One

Evolve (Whenever a creature enters the battlefield under your control, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Remove two +1/+1 counters from Experiment One: Regenerate Experiment One. (The next time this creature would be destroyed, instead tap it, remove it from combat, and heal all damage on it.)

Rootbound Crag

Rootbound Crag enters the battlefield tapped unless you control a Mountain or a Forest.
{T}: Add {R} or {G}.

Forest

Rubblebelt Raiders

Whenever Rubblebelt Raiders attacks, put a +1/+1 counter on it for each attacking creature you control.

Goblin Guide

Haste
Whenever Goblin Guide attacks, defending player reveals the top card of their library. If it's a land card, that player puts it into their hand.

Burning-Tree Emissary

When Burning-Tree Emissary enters the battlefield, add {R}{G}.

Thunderous Wrath

Thunderous Wrath deals 5 damage to any target.
Miracle {R} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)

Khalni Hydra

This spell costs {G} less to cast for each green creature you control.
Trample

Flinthoof Boar

Flinthoof Boar gets +1/+1 as long as you control a Mountain.
{R}: Flinthoof Boar gains haste until end of turn. (It can attack and {T} this turn.)

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Birds of Paradise

Ghalta, Primal Hunger

This spell costs {X} less to cast, where X is the total power of creatures you control.
Trample

Valley Rannet

Mountaincycling {2}, forestcycling {2} ({2}, Discard this card: Search your library for a Mountain or Forest card, reveal it, put it into your hand, then shuffle.)

Gigantosaurus

Zhur-Taa Goblin

Riot (This creature enters the battlefield with your choice of a +1/+1 counter or haste.)

Sunder Shaman

Sunder Shaman can't be blocked by more than one creature.
Whenever Sunder Shaman deals combat damage to a player, destroy target artifact or enchantment that player controls.

Xenagos, the Reveler

+1: Add X mana in any combination of {R} and/or {G}, where X is the number of creatures you control.
0: Create a 2/2 red and green Satyr creature token with haste.
−6: Exile the top seven cards of your library. You may put any number of creature and/or land cards from among them onto the battlefield.

Gruul Spellbreaker

Riot (This creature enters the battlefield with your choice of a +1/+1 counter or haste.)
Trample
As long as it's your turn, you and Gruul Spellbreaker have hexproof.

Llanowar Elves

Regisaur Alpha

Other Dinosaurs you control have haste.
When Regisaur Alpha enters the battlefield, create a 3/3 green Dinosaur creature token with trample.