Overwhelming Intellect

Counter target creature spell. Draw cards equal to that spell's mana value.

Azorius Chancery

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {W}{U}.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice this artifact: Draw a card.

Sleight of Hand

Look at the top two cards of your library. Put one of them into your hand and the other on the bottom of your library.

Serum Visions

Coralhelm Commander

Level up {1} ({1}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 2-3
3/3
Flying
LEVEL 4+
4/4
Flying
Other Merfolk creatures you control get +1/+1.

Counterspell

Coastal Piracy

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

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.

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Sigil Tracer

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

Rootwater Matriarch

{T}: Gain control of target creature for as long as that creature is enchanted.

Force of Will

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.
Counter target spell.

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.

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.

Merrow Commerce

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

Distant Melody

Choose a creature type. Draw a card for each permanent you control of that type.

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.

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.

Spreading Seas

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

Darksteel Ingot

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

Surgespanner

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

Silvergill Douser

{T}: Target creature gets -X/-0 until end of turn, where X is the number of Merfolk and/or Faeries you control.

Dissipate

Counter target spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Oona's Grace

Target player draws a card.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Swords to Plowshares

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

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

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.

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.

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.

Marble Diamond

This artifact enters tapped.
{T}: Add {W}.

Seahunter

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

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.

Stormtide Leviathan

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
All lands are Islands in addition to their other types.
Creatures without flying or islandwalk can't attack.

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.)

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.)

Empress Galina

{U}{U}, {T}: Gain control of target legendary permanent. (This effect lasts indefinitely.)

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.

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.

Deepchannel Mentor

Blue creatures you control can't be blocked.

Lord of Atlantis

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

Mind's Eye

Whenever an opponent draws a card, you may pay {1}. If you do, draw a card.

Stonybrook Schoolmaster

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

Sejiri Refuge

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {W} or {U}.

Reef Shaman

{T}: Target land becomes the basic land type 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.

Waterfront Bouncer

{U}, {T}, Discard a card: Return target creature to its owner's hand.

Seasinger

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

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.

Plains

Sky Diamond

This artifact enters tapped.
{T}: Add {U}.

Coat of Arms

Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)

Austere Command

Choose two —
• Destroy all artifacts.
• Destroy all enchantments.
• Destroy all creatures with mana value 3 or less.
• Destroy all creatures with mana value 4 or greater.

Negate

Scroll Thief

Whenever this creature deals combat damage to a player, draw a card.

Harpoon Sniper

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

Fallowsage

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

Enclave Cryptologist

Level up {1}{U} ({1}{U}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 1-2
0/1
{T}: Draw a card, then discard a card.
LEVEL 3+
0/1
{T}: Draw a card.

Sol Ring

Merrow Reejerey

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

Lonely Sandbar

This land enters tapped.
{T}: Add {U}.
Cycling {U} ({U}, Discard this card: Draw a card.)

Rootwater Thief

{U}: This creature gains flying until end of turn.
Whenever this creature deals combat damage to a player, you may pay {2}. If you do, search that player's library for a card and exile it, then the player shuffles.

Pristine Talisman

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.

Hallowed Fountain

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

Preordain

Scry 2, then draw a card. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Judge of Currents

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

Island

Riptide Laboratory

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

Back to Basics

Nonbasic lands don't untap during their controllers' untap steps.

Silvergill Adept

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