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.

Slippery Bogle

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

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.)

Island

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.

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.)

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.

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.)

Nettle Sentinel

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

Merrow Levitator

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

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.

Wistful Selkie

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.

Forest

Trip Noose

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.

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.

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.)

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.

Viridescent Wisps

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

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.

Dream Fracture

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

Cerulean Wisps

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