Windswept Heath

{T}, Pay 1 life, Sacrifice Windswept Heath: Search your library for a Forest or Plains card, put it onto the battlefield, then shuffle.

Breeding Pool

({T}: Add {G} or {U}.)
As Breeding Pool enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

Wrath of God

Destroy all creatures. They can't be regenerated.

Vanquisher's Banner

As Vanquisher's Banner enters the battlefield, choose a creature type.
Creatures you control of the chosen type get +1/+1.
Whenever you cast a creature spell of the chosen type, draw a card.

Temple Garden

({T}: Add {G} or {W}.)
As Temple Garden enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

Guardian Project

Whenever a nontoken creature enters the battlefield under your control, if it doesn't have the same name as another creature you control or a creature card in your graveyard, draw a card.

Talrand, Sky Summoner

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

Coralhelm Guide

{4}{U}: Target creature can't be blocked this turn.

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Merfolk Trickster

Flash
When Merfolk Trickster enters the battlefield, tap target creature an opponent controls. It loses all abilities until end of turn.

Llanowar Scout

{T}: You may put a land card from your hand onto the battlefield.

Prairie Stream

({T}: Add {W} or {U}.)
Prairie Stream enters the battlefield tapped unless you control two or more basic lands.

Benthic Biomancer

{1}{U}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.)
Whenever one or more +1/+1 counters are put on Benthic Biomancer, draw a card, then discard a card.

Tidespout Tyrant

Flying
Whenever you cast a spell, return target permanent to its owner's hand.

Birds of Paradise

Leyline of Anticipation

If Leyline of Anticipation is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Thirst for Meaning

Draw three cards. Then discard two cards unless you discard an enchantment card.

Polluted Delta

{T}, Pay 1 life, Sacrifice Polluted Delta: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

Hallowed Fountain

({T}: Add {W} or {U}.)
As Hallowed Fountain enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

Merrow Reejerey

Other Merfolk creatures you control get +1/+1.
Whenever you cast a Merfolk spell, you may tap or untap target permanent.

Island

Mother of Runes

{T}: Target creature you control gains protection from the color of your choice until end of turn.

Merfolk Sovereign

Other Merfolk creatures you control get +1/+1.
{T}: Target Merfolk creature can't be blocked this turn.

Crashing Tide

This spell has flash as long as you control a Merfolk.
Return target creature to its owner's hand.
Draw a card.

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.)

Harbinger of the Tides

You may cast Harbinger of the Tides as though it had flash if you pay {2} more to cast it. (You may cast it any time you could cast an instant.)
When Harbinger of the Tides enters the battlefield, you may return target tapped creature an opponent controls to its owner's hand.

Waterknot

Enchant creature
When Waterknot enters the battlefield, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Lord of Atlantis

Other Merfolk get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Vodalian Mage

{U}, {T}: Counter target spell unless its controller pays {1}.

Fblthp, the Lost

When Fblthp, the Lost enters the battlefield, draw a card. If it entered from your library or was cast from your library, draw two cards instead.
When Fblthp becomes the target of a spell, shuffle Fblthp into its owner's library.

Master of the Pearl Trident

Other Merfolk creatures you control get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Vizier of the Menagerie

You may look at the top card of your library any time.
You may cast creature spells from the top of your library.
You can spend mana of any type to cast creature spells.

Deeproot Champion

Whenever you cast a noncreature spell, put a +1/+1 counter on Deeproot Champion.

Mystic Sanctuary

({T}: Add {U}.)
Mystic Sanctuary enters the battlefield tapped unless you control three or more other Islands.
When Mystic Sanctuary enters the battlefield untapped, you may put target instant or sorcery card from your graveyard on top of your library.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Retreat to Coralhelm

Landfall — Whenever a land enters the battlefield under your control, choose one —
• You may tap or untap target creature.
• Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Forerunner of the Heralds

When Forerunner of the Heralds enters the battlefield, you may search your library for a Merfolk card, reveal it, then shuffle and put that card on top.
Whenever another Merfolk enters the battlefield under your control, put a +1/+1 counter on Forerunner of the Heralds.

Augur of Bolas

When Augur of Bolas enters the battlefield, look at the top three cards of your library. You may reveal an instant or sorcery card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

End-Raze Forerunners

Vigilance, trample, haste
When End-Raze Forerunners enters the battlefield, other creatures you control get +2/+2 and gain vigilance and trample until end of turn.

Mirror Entity

Changeling (This card is every creature type.)
{X}: Until end of turn, creatures you control have base power and toughness X/X and gain all creature types.

Sol Ring

Plains

Chulane, Teller of Tales

Vigilance
Whenever you cast a creature spell, draw a card, then you may put a land card from your hand onto the battlefield.
{3}, {T}: Return target creature you control to its owner's hand.

Jade Bearer

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

Master of Waves

Protection from red
Elemental creatures you control get +1/+1.
When Master of Waves enters the battlefield, create a number of 1/0 blue Elemental creature tokens equal to your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Phantasmal Image

You may have Phantasmal Image enter the battlefield as a copy of any creature on the battlefield, except it's an Illusion in addition to its other types and it has "When this creature becomes the target of a spell or ability, sacrifice it."

Flooded Strand

{T}, Pay 1 life, Sacrifice Flooded Strand: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.

Icon of Ancestry

As Icon of Ancestry enters the battlefield, choose a creature type.
Creatures you control of the chosen type get +1/+1.
{3}, {T}: Look at the top three cards of your library. You may reveal a creature card of the chosen type from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Sworn Guardian

Selesnya Sanctuary

Selesnya Sanctuary enters the battlefield tapped.
When Selesnya Sanctuary enters the battlefield, return a land you control to its owner's hand.
{T}: Add {G}{W}.

Generous Gift

Destroy target permanent. Its controller creates a 3/3 green Elephant creature token.

Thassa's Oracle

When Thassa's Oracle enters the battlefield, look at the top X cards of your library, where X is your devotion to blue. Put up to one of them on top of your library and the rest on the bottom of your library in a random order. If X is greater than or equal to the number of cards in your library, you win the game. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Silvergill Adept

As an additional cost to cast this spell, reveal a Merfolk card from your hand or pay {3}.
When Silvergill Adept enters the battlefield, draw a card.

Skyshroud Ranger

{T}: You may put a land card from your hand onto the battlefield. Activate only as a sorcery.

Mist-Cloaked Herald

Metallic Mimic

As Metallic Mimic enters the battlefield, choose a creature type.
Metallic Mimic is the chosen type in addition to its other types.
Each other creature you control of the chosen type enters the battlefield with an additional +1/+1 counter on it.

Herald's Horn

As Herald's Horn enters the battlefield, choose a creature type.
Creature spells you cast of the chosen type cost {1} less to cast.
At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

Faeburrow Elder

Vigilance
Faeburrow Elder gets +1/+1 for each color among permanents you control.
{T}: For each color among permanents you control, add one mana of that color.

Tatyova, Benthic Druid

Landfall — Whenever a land enters the battlefield under your control, you gain 1 life and draw a card.

Tempest Caller

When Tempest Caller enters the battlefield, tap all creatures target opponent controls.

Yavimaya Coast

{T}: Add {C}.
{T}: Add {G} or {U}. Yavimaya Coast deals 1 damage to you.

Seasinger

When you control no Islands, sacrifice Seasinger.
You may choose not to untap Seasinger during your untap step.
{T}: Gain control of target creature whose controller controls an Island for as long as you control Seasinger and Seasinger remains tapped.

Echo of Eons

Each player shuffles their hand and graveyard into their library, then draws seven cards.
Flashback {2}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Simic Growth Chamber

Simic Growth Chamber enters the battlefield tapped.
When Simic Growth Chamber enters the battlefield, return a land you control to its owner's hand.
{T}: Add {G}{U}.

Waterlogged Grove

{T}, Pay 1 life: Add {G} or {U}.
{1}, {T}, Sacrifice Waterlogged Grove: Draw a card.

Slinn Voda, the Rising Deep

Kicker {1}{U} (You may pay an additional {1}{U} as you cast this spell.)
When Slinn Voda, the Rising Deep enters the battlefield, if it was kicked, return all creatures to their owners' hands except for Merfolk, Krakens, Leviathans, Octopuses, and Serpents.

Vodalian Arcanist

{T}: Add {C}. Spend this mana only to cast an instant or sorcery spell.

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.

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.)

Cursecatcher

Sacrifice Cursecatcher: Counter target instant or sorcery spell unless its controller pays {1}.

Kumena's Speaker

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

Irregular Cohort

Changeling (This card is every creature type.)
When Irregular Cohort enters the battlefield, create a 2/2 colorless Shapeshifter creature token with changeling.

Merfolk Mistbinder

True-Name Nemesis

As True-Name Nemesis enters the battlefield, choose a player.
True-Name Nemesis has protection from the chosen player.

Mystic Snake

Flash
When Mystic Snake enters the battlefield, counter target spell.

Command Tower

Time Wipe

Return a creature you control to its owner's hand, then destroy all creatures.

Forest

Dovin's Veto

This spell can't be countered.
Counter target noncreature spell.

River Darter

River Darter can't be blocked by Dinosaurs.

Beastmaster Ascension

Whenever a creature you control attacks, you may put a quest counter on Beastmaster Ascension.
As long as Beastmaster Ascension has seven or more quest counters on it, creatures you control get +5/+5.