Jade Guardian

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
When Jade Guardian enters the battlefield, put a +1/+1 counter on target Merfolk you control.

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.

Herald of Secret Streams

Creatures you control with +1/+1 counters on them can't be blocked.

Merfolk Skydiver

Flying
When Merfolk Skydiver enters the battlefield, put a +1/+1 counter on target creature you control.
{3}{G}{U}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Deeproot Champion

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

Cryptolith Rite

Creatures you control have "{T}: Add one mana of any color."

Jadelight Ranger

When Jadelight Ranger enters the battlefield, it explores, then it explores again. (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. Then repeat this process.)

Wake Thrasher

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

Merrow Commerce

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

Empress Galina

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

Deepchannel Mentor

Blue creatures you control can't be blocked.

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.

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.

Mist-Cloaked Herald

Tishana's Wayfinder

When Tishana's Wayfinder 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.)

Thada Adel, Acquisitor

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Thada Adel, Acquisitor 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.

Seahunter

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

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.)

Combine Guildmage

{1}{G}, {T}: This turn, each creature you control enters the battlefield with an additional +1/+1 counter on it.
{1}{U}, {T}: Move a +1/+1 counter from target creature you control onto another target creature you control.

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.

Zegana, Utopian Speaker

When Zegana, Utopian Speaker enters the battlefield, if you control another creature with a +1/+1 counter on it, draw a card.
{4}{G}{U}: Adapt 4. (If this creature has no +1/+1 counters on it, put four +1/+1 counters on it.)
Each creature you control with a +1/+1 counter on it has trample.

Lord of Atlantis

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

Merfolk Mistbinder

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.

Vineshaper Mystic

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

River Sneak

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

Sol Ring

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.

Merfolk Looter

Murkfiend Liege

Other green creatures you control get +1/+1.
Other blue creatures you control get +1/+1.
Untap all green and/or blue creatures you control during each other player's untap step.

True-Name Nemesis

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

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.

Tatyova, Benthic Druid

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

Prime Speaker Zegana

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

Path of Ancestry

Path of Ancestry enters the battlefield 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.)

Surgespanner

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

Cold-Eyed Selkie

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Cold-Eyed Selkie deals combat damage to a player, you may draw that many 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.

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.)

Fallowsage

Whenever Fallowsage becomes tapped, you may draw a card.

Merrow Harbinger

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

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 the battlefield, draw a card for each creature you control.

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.

Vorel of the Hull Clade

{G}{U}, {T}: Double the number of each kind of counter on target artifact, creature, or land.

Merfolk Sovereign

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

Arcane Signet

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

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.

Cultivate

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.

Archmage's Charm

Choose one —
• Counter target spell.
• Target player draws two cards.
• Gain control of target nonland permanent with mana value 1 or less.

Sage of Fables

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

Jade Bearer

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

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.

Kiora's Follower

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.

Swift Warden

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

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.")

Counterspell

Deeproot Elite

Whenever another Merfolk enters the battlefield under your control, put a +1/+1 counter on target Merfolk you control.

Kumena's Speaker

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

Merrow Reejerey

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

Shapers of Nature

{3}{G}: Put a +1/+1 counter on target creature.
{2}{U}, Remove a +1/+1 counter from a creature you control: Draw a card.

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.

Seafloor Oracle

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

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.

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.)