Harpoon Sniper

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

Pemmin's Aura

Enchant creature
{U}: Untap enchanted creature.
{U}: Enchanted creature gains flying until end of turn.
{U}: Enchanted creature gains shroud until end of turn. (It can't be the target of spells or abilities.)
{1}: Enchanted creature gets +1/-1 or -1/+1 until end of turn.

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.)

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.

Raise the Palisade

Choose a creature type. Return all creatures that aren't of the chosen type to their owners' hands.

Spreading Seas

Enchant land
When this Aura enters, draw a card.
Enchanted land is an Island.

Drowner of Secrets

Tap an untapped Merfolk you control: Target player mills a card.

Urza's Rebuff

Choose one —
• Counter target spell.
• Tap up to two target creatures.

Kefnet's Monument

Blue creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, target creature an opponent controls doesn't untap during its controller's next untap step.

Cryptic Gateway

Tap two untapped creatures you control: You may put a creature card from your hand that shares a creature type with each creature tapped this way onto the battlefield.

Spectral Deluge

Return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.
Foretell {1}{U}{U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Plains

Merfolk Sovereign

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

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.

Citywide Bust

Destroy all creatures with toughness 4 or greater.

Springleaf Drum

{T}, Tap an untapped creature you control: Add one mana of any color.

River's Rebuke

Return all nonland permanents target player controls to their owner's hand.

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}.)

Stonybrook Angler

{1}{U}, {T}: You may tap or untap target creature.

Thada Adel, Acquisitor

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Thada Adel deals combat damage to a player, search that player's library for an artifact card and exile it. Then that player shuffles. Until end of turn, you may play that card.

Slinn Voda, the Rising Deep

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

Vodalian Hexcatcher

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

Adarkar Wastes

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

Holdout Settlement

{T}: Add {C}. ({C} represents colorless mana.)
{T}, Tap an untapped creature you control: Add one mana of any color.

Mutavault

{T}: Add {C}.
{1}: This land becomes a 2/2 creature with all creature types until end of turn. It's still a land.

Retraction Helix

Until end of turn, target creature gains "{T}: Return target nonland permanent to its owner's hand."

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.

Sand Squid

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
You may choose not to untap this creature during your untap step.
{T}: Tap target creature. That creature doesn't untap during its controller's untap step for as long as this creature remains tapped.

Benthicore

When this creature enters, create two 1/1 blue Merfolk Wizard creature tokens.
Tap two untapped Merfolk you control: Untap this creature. It gains shroud until end of turn. (It can't be the target of spells or abilities.)

Aura of Dominion

Enchant creature
{1}, Tap an untapped creature you control: Untap enchanted creature.

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.

Freed from the Real

Enchant creature
{U}: Tap enchanted creature.
{U}: Untap enchanted creature.

Sigil Tracer

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

Unclaimed Territory

As this land enters, choose a creature type.
{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type.

Seahunter

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

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}.

Thassa, Deep-Dwelling

Indestructible
As long as your devotion to blue is less than five, Thassa isn't a creature.
At the beginning of your end step, exile up to one other target creature you control, then return that card to the battlefield under your control.
{3}{U}: Tap another target creature.

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.

Mishra's Factory

{T}: Add {C}.
{1}: This land becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.
{T}: Target Assembly-Worker creature gets +1/+1 until end of turn.

Mistcaller

Sacrifice this creature: Until end of turn, if a nontoken creature would enter and it wasn't cast, exile it instead.

Wizard's Retort

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

High Tide

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

Tide Shaper

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

Merfolk Trickster

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

Dawn

Aftermath (Cast this spell only from your graveyard. Then exile it.)
Return all creature cards with power 2 or less from your graveyard to your hand.

Dusk

Destroy all creatures with power 3 or greater.

Dusk // Dawn

Seafloor Oracle

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

Veteran of the Depths

Whenever this creature becomes tapped, you may put a +1/+1 counter on it.

Merrow Commerce

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

Stonybrook Schoolmaster

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

Dread Statuary

{T}: Add {C}.
{4}: This land becomes a 4/2 Golem artifact creature until end of turn. It's still a land.

Sea Scryer

Hidden Strings

You may tap or untap target permanent, then you may tap or untap another target permanent.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Dramatic Reversal

Untap all nonland permanents you control.

Wake Thrasher

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

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.

Muddle the Mixture

Counter target instant or sorcery spell.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

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.

Surgespanner

Whenever this creature becomes tapped, you may pay {1}{U}. If you do, return target permanent to its owner's hand.

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.

Intruder Alarm

Creatures don't untap during their controllers' untap steps.
Whenever a creature enters, untap all creatures.

Paradise Mantle

Equipped creature has "{T}: Add one mana of any color."
Equip {1}

Mishra's Foundry

{T}: Add {C}.
{2}: This land becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.
{1}, {T}: Target attacking Assembly-Worker gets +2/+2 until end of turn.

Fallowsage

Whenever this creature becomes tapped, you may draw a card.

River Sneak

This creature can't be blocked.
Whenever another Merfolk you control enters, this creature gets +1/+1 until end of turn.

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.)

Azorius Keyrune

{T}: Add {W} or {U}.
{W}{U}: This artifact becomes a 2/2 white and blue Bird artifact creature with flying until end of turn.

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 Pilgrimage

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

Lullmage Mentor

Whenever a spell or ability you control counters a spell, you may create a 1/1 blue Merfolk creature token.
Tap seven untapped Merfolk you control: Counter target spell.

Grimoire Thief

Whenever this creature becomes tapped, exile the top three cards of target opponent's library face down.
You may look at cards exiled with this creature.
{U}, Sacrifice this creature: Turn all cards exiled with this creature face up. Counter all spells with those names.

Make a Stand

Creatures you control get +1/+0 and gain indestructible until end of turn. (Damage and effects that say "destroy" don't destroy them.)

Scourge of Fleets

When this creature enters, return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.

Curse of the Swine

Exile X target creatures. For each creature exiled this way, its controller creates a 2/2 green Boar creature token.

Cultivator's Caravan

{T}: Add one mana of any color.
Crew 3 (Tap any number of creatures you control with total power 3 or more: This Vehicle becomes an artifact creature until end of turn.)

Aquitect's Will

Put a flood counter on target land. That land is an Island in addition to its other types for as long as it has a flood counter on it. If you control a Merfolk, draw a card.

Island

Merrow Reejerey

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

Streambed Aquitects

{T}: Target Merfolk creature gets +1/+1 and gains islandwalk until end of turn. (It can't be blocked as long as defending player controls an Island.)
{T}: Target land becomes an Island until end of turn.

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.

Disenchant

Survivors' Encampment

{T}: Add {C}.
{T}, Tap an untapped creature you control: Add one mana of any color.

Summon: Leviathan

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Return each creature that isn't a Kraken, Leviathan, Merfolk, Octopus, or Serpent to its owner's hand.
II, III — Until end of turn, whenever a Kraken, Leviathan, Merfolk, Octopus, or Serpent attacks, draw a card.
Ward {2}

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.)