Sturdy Hatchling

This creature enters with four -1/-1 counters on it.
{G/U}: This creature gains shroud until end of turn. (It can't be the target of spells or abilities.)
Whenever you cast a green spell, remove a -1/-1 counter from this creature.
Whenever you cast a blue spell, remove a -1/-1 counter from this creature.

Favor of the Overbeing

Enchant creature
As long as enchanted creature is green, it gets +1/+1 and has vigilance.
As long as enchanted creature is blue, it gets +1/+1 and has flying.

Cerulean Wisps

Target creature becomes blue until end of turn. Untap that creature.
Draw a card.

Wistful Selkie

Wickerbough Elder

This creature enters with a -1/-1 counter on it.
{G}, Remove a -1/-1 counter from this creature: Destroy target artifact or enchantment.

Drowner Initiate

Whenever a player casts a blue spell, you may pay {1}. If you do, target player mills two cards.

Selkie Hedge-Mage

When this creature enters, if you control two or more Forests, you may gain 3 life.
When this creature enters, if you control two or more Islands, you may return target tapped creature to its owner's hand.

Invert the Skies

Creatures your opponents control lose flying until end of turn if {G} was spent to cast this spell, and creatures you control gain flying until end of turn if {U} was spent to cast this spell. (Do both if {G}{U} was spent.)

Monstrify

Target creature gets +4/+4 until end of turn.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Trip Noose

Merrow Levitator

{T}: Target creature gains flying until end of turn.
Whenever you cast a blue spell, you may untap this creature.

Groundling Pouncer

{G/U}: This creature gets +1/+3 and gains flying until end of turn. Activate only once each turn and only if an opponent controls a creature with flying.

Nettle Sentinel

This creature doesn't untap during your untap step.
Whenever you cast a green spell, you may untap this creature.

Snakeform

Until end of turn, target creature loses all abilities and becomes a green Snake with base power and toughness 1/1.
Draw a card.

Dream Fracture

Counter target spell. Its controller draws a card.
Draw a card.

Viridescent Wisps

Target creature becomes green and gets +1/+0 until end of turn.
Draw a card.

Forest

Shorecrasher Mimic

Whenever you cast a spell that's both green and blue, this creature has base power and toughness 5/3 until end of turn and gains trample until end of turn.

Slippery Bogle

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

Fable of Wolf and Owl

Whenever you cast a green spell, you may create a 2/2 green Wolf creature token.
Whenever you cast a blue spell, you may create a 1/1 blue Bird creature token with flying.

Spitting Image

Create a token that's a copy of target creature.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Grazing Kelpie

{G/U}, Sacrifice this creature: Put target card from a graveyard on the bottom of its owner's library.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Nurturer Initiate

Whenever a player casts a green spell, you may pay {1}. If you do, target creature gets +1/+1 until end of turn.