Crown of Ascension

Enchant creature
Enchanted creature has flying.
Sacrifice Crown of Ascension: Enchanted creature and other creatures that share a creature type with it gain flying until end of turn.

Riverwise Augur

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

Unclaimed Territory

As Unclaimed Territory 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.

Coastal Piracy

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

Counterspell

Levitation

Riptide Pilferer

Whenever Riptide Pilferer deals combat damage to a player, that player discards a card.
Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Grave Sifter

When Grave Sifter enters, each player chooses a creature type and returns any number of cards of that type from their graveyard to their hand.

Jungleborn Pioneer

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

Capsize

Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Return target permanent to its owner's hand.

Thought Vessel

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

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.)

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.)

Vanquisher's Banner

As Vanquisher's Banner enters, 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.

Merrow Harbinger

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

Kodama's Reach

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Thornwood Falls

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

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.

Cultivate

True-Name Nemesis

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

Favorable Winds

Creatures you control with flying get +1/+1.

Windrider Patrol

Flying
Whenever Windrider Patrol deals combat damage to a player, 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.)

Temple of Mystery

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 {G} or {U}.

Borrowing 100,000 Arrows

Draw a card for each tapped creature target opponent controls.

Forest

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.)

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Eternal Witness

When Eternal Witness enters, you may return target card from your graveyard to your hand.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Archetype of Imagination

Creatures you control have flying.
Creatures your opponents control lose flying and can't have or gain flying.

Tishana, Voice of Thunder

Tishana, Voice of Thunder's power and toughness are each equal to the number of cards in your hand.
You have no maximum hand size.
When Tishana enters, draw a card for each creature you control.

Swift Warden

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

Merrow Commerce

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

Merfolk Sovereign

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

Venser's Journal

You have no maximum hand size.
At the beginning of your upkeep, you gain 1 life for each card in your hand.

Lumbering Falls

Lumbering Falls enters tapped.
{T}: Add {G} or {U}.
{2}{G}{U}: Lumbering Falls becomes a 3/3 green and blue Elemental creature with hexproof until end of turn. It's still a land.

Wonder

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

Winged Temple of Orazca

(Transforms from Hadana's Climb.)
{T}: Add one mana of any color.
{1}{G}{U}, {T}: Target creature you control gains flying and gets +X/+X until end of turn, where X is its power.

Hadana's Climb

At the beginning of combat on your turn, put a +1/+1 counter on target creature you control. Then if that creature has three or more +1/+1 counters on it, transform Hadana's Climb.

Hadana's Climb // Winged Temple of Orazca

Throne of the God-Pharaoh

At the beginning of your end step, each opponent loses life equal to the number of tapped creatures you control.

Kindred Discovery

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

Sword of the Animist

Equipped creature gets +1/+1.
Whenever equipped creature attacks, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Equip {2}

Flooded Grove

{T}: Add {C}.
{G/U}, {T}: Add {G}{G}, {G}{U}, or {U}{U}.

Intruder Alarm

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

Gaea's Skyfolk

River Sneak

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

Merrow Reejerey

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

Prime Speaker Zegana

Prime Speaker Zegana enters with X +1/+1 counters on it, where X is the greatest power among other creatures you control.
When Prime Speaker Zegana enters, draw cards equal to its power.

Jace Beleren

+2: Each player draws a card.
−1: Target player draws a card.
−10: Target player mills twenty cards.

Kumena, Tyrant of Orazca

Tap another untapped Merfolk you control: Kumena, Tyrant of Orazca can't be blocked this turn.
Tap three untapped Merfolk you control: Draw a card.
Tap five untapped Merfolk you control: Put a +1/+1 counter on each Merfolk you control.

Watertrap Weaver

When Watertrap Weaver enters, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

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.

Skyline Cascade

Skyline Cascade enters tapped.
When Skyline Cascade enters, target creature an opponent controls doesn't untap during its controller's next untap step.
{T}: Add {U}.

Hinterland Harbor

Hinterland Harbor enters tapped unless you control a Forest or an Island.
{T}: Add {G} or {U}.

Seafloor Oracle

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

Forerunner of the Heralds

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

Yavimaya Coast

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

Sleep

Tap all creatures target player controls. Those creatures don't untap during that player's next untap step.

Breeding Pool

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

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.

Merfolk Mistbinder

Cyclonic Rift

Return target nonland permanent you don't control to its owner's hand.
Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Tempest Caller

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

Simic Growth Chamber

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

Vineshaper Mystic

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

Beast Within

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

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Awakening

At the beginning of each upkeep, untap all creatures and lands.

Reality Shift

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)

Thrasios, Triton Hero

{4}: Scry 1, then reveal the top card of your library. If it's a land card, put it onto the battlefield tapped. Otherwise, draw a card.
Partner (You can have two commanders if both have partner.)

Krosan Grip

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Destroy target artifact or enchantment.

Island

Command Tower

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

Gravitational Shift

Creatures with flying get +2/+0.
Creatures without flying get -2/-0.

Worldly Tutor

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Lord of Atlantis

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