Colossal Might

Target creature gets +4/+2 and gains trample until end of turn.

Blanchwood Armor

Enchant creature
Enchanted creature gets +1/+1 for each Forest you control.

Nykthos, Shrine to Nyx

{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Become Immense

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Target creature gets +6/+6 until end of turn.

Enlarge

Target creature gets +7/+7 and gains trample until end of turn. It must be blocked this turn if able. (A creature with trample can deal excess combat damage to the player or planeswalker it's attacking.)

Silhana Ledgewalker

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Silhana Ledgewalker can't be blocked except by creatures with flying.

Dungrove Elder

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Dungrove Elder's power and toughness are each equal to the number of Forests you control.

Slippery Bogle

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Gladecover Scout

Hare Raising

Target creature you control gains vigilance and gets +X/+X until end of turn, where X is the number of creatures you control.

Pollen-Shield Hare

Pollen-Shield Hare // Hare Raising

Ambush Viper

Primal Bellow

Target creature gets +1/+1 until end of turn for each Forest you control.

Bassara Tower Archer

Branching Evolution

If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on that creature instead.

Might of Old Krosa

Target creature gets +2/+2 until end of turn. If you cast this spell during your main phase, that creature gets +4/+4 until end of turn instead.

Titanic Growth

Target creature gets +4/+4 until end of turn.

Tyvar's Stand

Target creature you control gets +X/+X and gains hexproof and indestructible until end of turn. (A creature with hexproof and indestructible can't be the target of spells or abilities your opponents control. Damage and effects that say "destroy" don't destroy it.)

Giant Growth

Target creature gets +3/+3 until end of turn.

Rancor

Enchant creature
Enchanted creature gets +2/+0 and has trample.
When Rancor is put into a graveyard from the battlefield, return Rancor to its owner's hand.

Garruk, Unleashed

+1: Up to one target creature gets +3/+3 and gains trample until end of turn.
−2: Create a 3/3 green Beast creature token. Then if an opponent controls more creatures than you, put a loyalty counter on Garruk, Unleashed.
−7: You get an emblem with "At the beginning of your end step, you may search your library for a creature card, put it onto the battlefield, then shuffle."

Forest

Leering Emblem

Whenever you cast a spell, equipped creature gets +2/+2 until end of turn.
Equip {2}

Groundswell

Target creature gets +2/+2 until end of turn.
Landfall — If you had a land enter the battlefield under your control this turn, that creature gets +4/+4 until end of turn instead.

Primal Might

Target creature you control gets +X/+X until end of turn. Then it fights up to one target creature you don't control. (Each deals damage equal to its power to the other.)