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.)

River Darter

River Darter can't be blocked by Dinosaurs.

Forest

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.

Jungleborn Pioneer

When Jungleborn Pioneer enters the battlefield, create a 1/1 blue Merfolk creature token with hexproof. (It can't be the target of spells or abilities your opponents control.)

Shapers' Sanctuary

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

Biolume Serpent

Sacrifice two Islands: Biolume Serpent can't be blocked this turn.

Biolume Egg

Defender
When Biolume Egg enters the battlefield, scry 2.
When you sacrifice Biolume Egg, return it to the battlefield transformed under its owner's control at the beginning of the next end step.

Biolume Egg // Biolume Serpent

Spell Stutter

Counter target spell unless its controller pays {2} plus an additional {1} for each Faerie you control.

Aspirant's Ascent

Until end of turn, target creature gets +1/+3 and gains flying and toxic 1. (Players dealt combat damage by that creature also get a poison counter.)

Water Wings

Until end of turn, target creature you control has base power and toughness 4/4 and gains flying and hexproof. (It can't be the target of spells or abilities your opponents control.)

Storm Sculptor

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

Plummet

Hunter's Edge

Put a +1/+1 counter on target creature you control. Then that creature deals damage equal to its power to target creature you don't control.

Bestial Bloodline

Enchant creature
Enchanted creature gets +2/+2.
{4}{G}: Return Bestial Bloodline from your graveyard to your hand.

Island

As Foretold

At the beginning of your upkeep, put a time counter on As Foretold.
Once each turn, you may pay {0} rather than pay the mana cost for a spell you cast with mana value X or less, where X is the number of time counters on As Foretold.

Swift Warden

Flash
When Swift Warden enters the battlefield, target Merfolk you control gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

One With the Wind

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

Wavesifter

Flying
When Wavesifter enters the battlefield, investigate twice. (To investigate, create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Evoke {G}{U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters the battlefield.)

Royal Treatment

Target creature you control gains hexproof until end of turn. Create a Royal Role token attached to that creature. (If you control another Role on it, put that one into the graveyard. Enchanted creature gets +1/+1 and has ward {1}.)

Riverwise Augur

When Riverwise Augur enters the battlefield, draw three cards, then put two cards from your hand on top of your library in any order.

Kumena's Speaker

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

Scuttletide

{1}, Discard a card: Create a 0/3 blue Crab creature token.
Delirium — Crabs you control get +1/+1 as long as there are four or more card types among cards in your graveyard.

Spreading Seas

Enchant land
When Spreading Seas enters the battlefield, draw a card.
Enchanted land is an Island.

Tide Shaper

Kicker {1} (You may pay an additional {1} as you cast this spell.)
When Tide Shaper enters the battlefield, if it was kicked, target land becomes an Island for as long as Tide Shaper remains on the battlefield.
Tide Shaper gets +1/+1 as long as an opponent controls an Island.

Merfolk Coralsmith

{1}: Merfolk Coralsmith gets +1/-1 until end of turn.
When Merfolk Coralsmith dies, scry 2.

Headwater Sentries

Restless Vinestalk

Restless Vinestalk enters the battlefield tapped.
{T}: Add {G} or {U}.
{3}{G}{U}: Until end of turn, Restless Vinestalk becomes a 5/5 green and blue Plant creature with trample. It's still a land.
Whenever Restless Vinestalk attacks, up to one other target creature has base power and toughness 3/3 until end of turn.

New Horizons

Enchant land
When New Horizons enters the battlefield, put a +1/+1 counter on target creature you control.
Enchanted land has "{T}: Add two mana of any one color."

Orazca Relic

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
{T}: Add {C}.
{T}, Sacrifice Orazca Relic: You gain 3 life and draw a card. Activate only if you have the city's blessing.

Deeproot Elite

Whenever another Merfolk enters the battlefield under your control, put a +1/+1 counter on target Merfolk you control.

Jade Bearer

When Jade Bearer enters the battlefield, put a +1/+1 counter on another target Merfolk you control.

Enter the Unknown

Target creature you control 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 the creature, then put the card back or put it into your graveyard.)
You may play an additional land this turn.

Vineshaper Mystic

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

Giltgrove Stalker

Giltgrove Stalker can't be blocked by creatures with power 2 or less.

Wose Pathfinder

{T}: Add one mana of any color.
{6}{G}, {T}: Another target creature gets +3/+3 and gains trample until end of turn.

Emergent Growth

Target creature gets +5/+5 until end of turn and must be blocked this turn if able.

Mist-Cloaked Herald

Bramble Armor

When Bramble Armor enters the battlefield, attach it to target creature you control.
Equipped creature gets +2/+1.
Equip {4} ({4}: Attach to target creature you control. Equip only as a sorcery.)

Troyan, Gutsy Explorer

{T}: Add {G}{U}. Spend this mana only to cast spells with mana value 5 or greater or spells with {X} in their mana costs.
{U}, {T}: Draw a card, then discard a card.