Merrow Harbinger

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
When this creature enters, you may search your library for a Merfolk card, reveal it, then shuffle and put that card on top.

Arcane Signet

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

Wake Thrasher

Whenever a permanent you control becomes untapped, this creature gets +1/+1 until end of turn.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Darksteel Ingot

Indestructible (Effects that say "destroy" don't destroy this artifact.)
{T}: Add one mana of any color.

Ghostly Prison

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Mist-Cloaked Herald

Puresight Merrow

{W/U}, {Q}: Look at the top card of your library. You may exile that card. ({Q} is the untap symbol.)

Tolaria West

This land enters tapped.
{T}: Add {U}.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with mana value 0, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Cosi's Trickster

Whenever an opponent shuffles their library, you may put a +1/+1 counter on this creature.

Wayfarer's Bauble

{2}, {T}, Sacrifice this artifact: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Svyelun of Sea and Sky

Svyelun has indestructible as long as you control at least two other Merfolk.
Whenever Svyelun attacks, draw a card.
Other Merfolk you control have ward {1}. (Whenever another Merfolk you control becomes the target of a spell or ability an opponent controls, counter it unless that player pays {1}.)

Island

Path of Ancestry

This land enters tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

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.

Generous Gift

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

Wizard's Retort

This spell costs {1} less to cast if you control a Wizard.
Counter target spell.

Coastal Piracy

Whenever a creature you control deals combat damage to an opponent, you may draw a card.

Archaeomancer's Map

When this artifact enters, search your library for up to two basic Plains cards, reveal them, put them into your hand, then shuffle.
Whenever a land an opponent controls enters, if that player controls more lands than you, you may put a land card from your hand onto the battlefield.

True-Name Nemesis

As this creature enters, choose a player.
This creature has protection from the chosen player.

Stonybrook Banneret

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Merfolk spells and Wizard spells you cast cost {1} less to cast.

Riptide Laboratory

{T}: Add {C}.
{1}{U}, {T}: Return target Wizard you control to its owner's hand.

Wanderwine Prophets

Champion a Merfolk (When this enters, sacrifice it unless you exile another Merfolk you control. When this leaves the battlefield, that card returns to the battlefield.)
Whenever this creature deals combat damage to a player, you may sacrifice a Merfolk. If you do, take an extra turn after this one.

Teferi's Protection

Until your next turn, your life total can't change and you gain protection from everything. All permanents you control phase out. (While they're phased out, they're treated as though they don't exist. They phase in before you untap during your untap step.)
Exile Teferi's Protection.

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Vedalken Aethermage

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, return target Sliver to its owner's hand.
Wizardcycling {3} ({3}, Discard this card: Search your library for a Wizard card, reveal it, put it into your hand, then shuffle.)

Sage's Dousing

Counter target spell unless its controller pays {3}. If you control a Wizard, draw a card.

Stonybrook Schoolmaster

Whenever this creature becomes tapped, you may create a 1/1 blue Merfolk Wizard creature token.

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Sage of Fables

Each other Wizard creature you control enters with an additional +1/+1 counter on it.
{2}, Remove a +1/+1 counter from a creature you control: Draw a card.

Merrow Reejerey

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

Deepchannel Mentor

Blue creatures you control can't be blocked.

Talisman of Progress

{T}: Add {C}.
{T}: Add {W} or {U}. This artifact deals 1 damage to you.

Harbinger of the Seas

Command Tower

Seahunter

{3}, {T}: Search your library for a Merfolk permanent card, put it onto the battlefield, then shuffle.

Terramorphic Expanse

{T}, Sacrifice this land: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Illusionist's Bracers

Whenever an ability of equipped creature is activated, if it isn't a mana ability, copy that ability. You may choose new targets for the copy.
Equip {3}

Aether Vial

At the beginning of your upkeep, you may put a charge counter on this artifact.
{T}: You may put a creature card with mana value equal to the number of charge counters on this artifact from your hand onto the battlefield.

Return to Dust

Exile target artifact or enchantment. If you cast this spell during your main phase, you may exile up to one other target artifact or enchantment.

Emperor Mihail II

You may look at the top card of your library any time.
You may cast Merfolk spells from the top of your library.
Whenever you cast a Merfolk spell, you may pay {1}. If you do, create a 1/1 blue Merfolk creature token.

Door of Destinies

As this artifact enters, choose a creature type.
Whenever you cast a spell of the chosen type, put a charge counter on this artifact.
Creatures you control of the chosen type get +1/+1 for each charge counter on this artifact.

Prairie Stream

({T}: Add {W} or {U}.)
This land enters tapped unless you control two or more basic lands.

Deeproot Pilgrimage

Whenever one or more nontoken Merfolk you control become tapped, create a 1/1 blue Merfolk creature token with hexproof.

Supreme Verdict

This spell can't be countered.
Destroy all creatures.

Evolving Wilds

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice this artifact: Draw a card.

Seafloor Oracle

Whenever a Merfolk you control deals combat damage to a player, draw a card.

Merfolk Sovereign

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

Sol Ring

Merfolk Trickster

Flash
When this creature enters, tap target creature an opponent controls. It loses all abilities until end of turn.

Reliquary Tower

Master of Waves

Protection from red
Elemental creatures you control get +1/+1.
When this creature enters, 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.)

Gilded Lotus

Mist Dancer

Flying
Other Merfolk you control get +1/+0 and have flying.
Encore {5}{U}{U} ({5}{U}{U}, Exile this card from your graveyard: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Thieving Skydiver

Kicker {X}. X can't be 0. (You may pay an additional {X} as you cast this spell.)
Flying
When this creature enters, if it was kicked, gain control of target artifact with mana value X or less. If that artifact is an Equipment, attach it to this creature.

Azorius Signet

Merrow Commerce

At the beginning of your end step, untap all Merfolk you control.

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.)

Delney, Streetwise Lookout

Creatures you control with power 2 or less can't be blocked by creatures with power 3 or greater.
If an ability of a creature you control with power 2 or less triggers, that ability triggers an additional time.

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.

Land Tax

At the beginning of your upkeep, if an opponent controls more lands than you, you may search your library for up to three basic land cards, reveal them, put them into your hand, then shuffle.

Plains

Temple of Enlightenment

This land enters tapped.
When this land enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)
{T}: Add {W} or {U}.

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Render Silent

Counter target spell. Its controller can't cast spells this turn.

Propaganda

Summon the School

Create two 1/1 blue Merfolk Wizard creature tokens.
Tap four untapped Merfolk you control: Return this card from your graveyard to your hand.

Sygg, River Guide

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
{1}{W}: Target Merfolk you control gains protection from the color of your choice until end of turn.

Thassa, God of the Sea

Indestructible
As long as your devotion to blue is less than five, Thassa isn't a creature. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)
At the beginning of your upkeep, scry 1.
{1}{U}: Target creature you control can't be blocked this turn.

Harpoon Sniper

{W}, {T}: This creature deals X damage to target attacking or blocking creature, where X is the number of Merfolk you control.

Patchwork Banner

As this artifact enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
{T}: Add one mana of any color.

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.)

Vodalian Hexcatcher

Flash
Other Merfolk you control get +1/+1.
Sacrifice a Merfolk: Counter target noncreature spell unless its controller pays {1}.

Herald's Horn

As this artifact enters, 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.

Judge of Currents

Whenever a Merfolk you control becomes tapped, you may gain 1 life.

Sigil Tracer

{1}{U}, Tap two untapped Wizards you control: Copy target instant or sorcery spell. You may choose new targets for the copy.

Negate

Tishana's Tidebinder

Flash
When this creature enters, counter up to one target activated or triggered ability. If an ability of an artifact, creature, or planeswalker is countered this way, that permanent loses all abilities for as long as this creature remains on the battlefield. (Mana abilities can't be targeted.)

True Conviction

Creatures you control have double strike and lifelink.

Counterspell

Wanderwine Hub

As this land enters, you may reveal a Merfolk card from your hand. If you don't, this land enters tapped.
{T}: Add {W} or {U}.

Vodalian Wave-Knight

Whenever you draw a card, put a +1/+1 counter on each other Merfolk and/or Knight you control.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Wrath of God

Destroy all creatures. They can't be regenerated.

Kindred Discovery

As this enchantment enters, choose a creature type.
Whenever a creature you control of the chosen type enters or attacks, draw a card.

Lord of Atlantis

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