River Sneak

River Sneak can't be blocked.
Whenever another Merfolk enters the battlefield under your control, River Sneak gets +1/+1 until end of turn.

Deeproot Warrior

Whenever Deeproot Warrior becomes blocked, it gets +1/+1 until end of turn.

Shaper Apprentice

Shaper Apprentice has flying as long as you control another Merfolk.

Dive Down

Target creature you control gets +0/+3 and gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Vineshaper Mystic

When Vineshaper Mystic enters the battlefield, put a +1/+1 counter on each of up to two target Merfolk you control.

Blossom Dryad

Blinding Fog

Prevent all damage that would be dealt to creatures this turn. Creatures you control gain hexproof until end of turn. (They can't be the targets of spells or abilities your opponents control.)

Kumena's Speaker

Kumena's Speaker gets +1/+1 as long as you control another Merfolk or an Island.

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.

Verdant Rebirth

Until end of turn, target creature gains "When this creature dies, return it to its owner's hand."
Draw a card.

Wind Strider

Talrand, Sky Summoner

Whenever you cast an instant or sorcery spell, create a 2/2 blue Drake creature token with flying.

Woodland Stream

Woodland Stream enters the battlefield tapped.
{T}: Add {G} or {U}.

Merfolk Branchwalker

When Merfolk Branchwalker enters the battlefield, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Headwater Sentries

Kopala, Warden of Waves

Spells your opponents cast that target a Merfolk you control cost {2} more to cast.
Abilities your opponents activate that target a Merfolk you control cost {2} more to activate.

Deeproot Waters

Whenever you cast a Merfolk spell, create a 1/1 blue Merfolk creature token with hexproof. (A creature with hexproof can't be the target of spells or abilities your opponents control.)

Run Aground

Put target artifact or creature on top of its owner's library.

Storm Sculptor

Storm Sculptor can't be blocked.
When Storm Sculptor enters the battlefield, return a creature you control to its owner's hand.

Air Elemental

Jade Guardian

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

One With the Wind

Enchant creature
Enchanted creature gets +2/+2 and has flying.

Watertrap Weaver

When Watertrap Weaver enters the battlefield, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

River Heralds' Boon

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

Forest

Shapers' Sanctuary

Whenever a creature you control becomes the target of a spell or ability an opponent controls, you may draw a card.

Waker of the Wilds

{X}{G}{G}: Put X +1/+1 counters on target land you control. That land becomes a 0/0 Elemental creature with haste. It's still a land.

Tishana's Wayfinder

When Tishana's Wayfinder enters the battlefield, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Sentinel Totem

When Sentinel Totem enters the battlefield, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)
{T}, Exile Sentinel Totem: Exile all graveyards.