Forest

Vineshaper Mystic

When this creature enters, put a +1/+1 counter on each of up to two target Merfolk you control.

Air Elemental

Deeproot Warrior

Whenever this creature becomes blocked, it gets +1/+1 until end of turn.

Shaper Apprentice

This creature has flying as long as you control another Merfolk.

Jade Guardian

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
When this creature enters, put a +1/+1 counter on target Merfolk you control.

Island

Grasping Current

Return up to two target creatures to their owner's hand.
Search your library and/or graveyard for a card named Jace, Ingenious Mind-Mage, reveal it, and put it into your hand. If you searched your library this way, shuffle.

Herald of Secret Streams

Creatures you control with +1/+1 counters on them can't be blocked.

Shapers of Nature

{3}{G}: Put a +1/+1 counter on target creature.
{2}{U}, Remove a +1/+1 counter from a creature you control: Draw a card.

Headwater Sentries

Jace's Sentinel

As long as you control a Jace planeswalker, this creature gets +1/+0 and can't be blocked.

Jace, Ingenious Mind-Mage

+1: Draw a card.
+1: Untap all creatures you control.
−9: Gain control of up to three target creatures.

Castaway's Despair

Enchant creature
When this Aura enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Kumena's Speaker

This creature gets +1/+1 as long as you control another Merfolk or an Island.

Fleet Swallower

Whenever this creature attacks, target player mills half their library, rounded up.

Tempest Caller

When this creature enters, tap all creatures target opponent controls.

Jungle Delver

{3}{G}: Put a +1/+1 counter on this creature.

Woodland Stream

This land enters tapped.
{T}: Add {G} or {U}.

River Heralds' Boon

Put a +1/+1 counter on target creature and a +1/+1 counter on up to one target Merfolk.