Managorger Hydra

Trample
Whenever a player casts a spell, put a +1/+1 counter on Managorger Hydra.

Heroes' Bane

Heroes' Bane enters the battlefield with four +1/+1 counters on it.
{2}{G}{G}: Put X +1/+1 counters on Heroes' Bane, where X is its power.

Elemental Bond

Whenever a creature with power 3 or greater enters the battlefield under your control, draw a card.

Elvish Mystic

Reclamation Sage

When Reclamation Sage enters the battlefield, you may destroy target artifact or enchantment.

Gravity Well

Whenever a creature with flying attacks, it loses flying until end of turn.

Polukranos, World Eater

{X}{X}{G}: Monstrosity X. (If this creature isn't monstrous, put X +1/+1 counters on it and it becomes monstrous.)
When Polukranos, World Eater becomes monstrous, it deals X damage divided as you choose among any number of target creatures your opponents control. Each of those creatures deals damage equal to its power to Polukranos.

Miming Slime

Create an X/X green Ooze creature token, where X is the greatest power among creatures you control.

Khalni Hydra

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

Caustic Caterpillar

{1}{G}, Sacrifice Caustic Caterpillar: Destroy target artifact or enchantment.

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Giant Growth

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

Aspect of Hydra

Target creature gets +X/+X until end of turn, where X is your devotion to green. (Each {G} in the mana costs of permanents you control counts toward your devotion to green.)

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.)

Somberwald Sage

{T}: Add three mana of any one color. Spend this mana only to cast creature spells.

Plummet

Wing Puncture

Target creature you control deals damage equal to its power to target creature with flying.

Rosheen Meanderer

{T}: Add {C}{C}{C}{C}. Spend this mana only on costs that contain {X}.

Reclaiming Vines

Destroy target artifact, enchantment, or land.

Aerial Predation

Destroy target creature with flying. You gain 2 life.

Mistcutter Hydra

This spell can't be countered.
Haste, protection from blue
Mistcutter Hydra enters the battlefield with X +1/+1 counters on it.

Increasing Savagery

Put five +1/+1 counters on target creature. If this spell was cast from a graveyard, put ten +1/+1 counters on that creature instead.
Flashback {5}{G}{G} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Slice in Twain

Destroy target artifact or enchantment.
Draw a card.

Protean Hydra

Protean Hydra enters the battlefield with X +1/+1 counters on it.
If damage would be dealt to Protean Hydra, prevent that damage and remove that many +1/+1 counters from it.
Whenever a +1/+1 counter is removed from Protean Hydra, put two +1/+1 counters on it at the beginning of the next end step.

Back to Nature

Nessian Wilds Ravager

Tribute 6 (As this creature enters the battlefield, an opponent of your choice may put six +1/+1 counters on it.)
When Nessian Wilds Ravager enters the battlefield, if tribute wasn't paid, you may have Nessian Wilds Ravager fight another target creature. (Each deals damage equal to its power to the other.)