Stomping Ground

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

Forest

Atarka, World Render

Flying, trample
Whenever a Dragon you control attacks, it gains double strike until end of turn.

Hobgoblin Captain

Pack tactics — Whenever Hobgoblin Captain attacks, if you attacked with creatures with total power 6 or greater this combat, Hobgoblin Captain gains first strike until end of turn.

Terror of Mount Velus

Flying, double strike
When Terror of Mount Velus enters the battlefield, creatures you control gain double strike until end of turn.

Werewolf Pack Leader

Pack tactics — Whenever Werewolf Pack Leader attacks, if you attacked with creatures with total power 6 or greater this combat, draw a card.
{3}{G}: Until end of turn, Werewolf Pack Leader has base power and toughness 5/3, gains trample, and isn't a Human.

Scale Up

Until end of turn, target creature you control becomes a green Wurm with base power and toughness 6/4.
Overload {4}{G}{G} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Mountain

Rootbound Crag

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

Tormenting Voice

As an additional cost to cast this spell, discard a card.
Draw two cards.

Minion of the Mighty

Menace
Pack tactics — Whenever Minion of the Mighty attacks, if you attacked with creatures with total power 6 or greater this combat, you may put a Dragon creature card from your hand onto the battlefield tapped and attacking.