Merfolk Traders

When Merfolk Traders enters, draw a card, then discard a card.

Merfolk of the Pearl Trident

Remove Soul

Blockade Runner

{U}: Blockade Runner can't be blocked this turn.

Merfolk Seer

When Merfolk Seer dies, you may pay {1}{U}. If you do, draw a card.

Tidal Influence

Cast this spell only if no permanents named Tidal Influence are on the battlefield.
Tidal Influence enters with a tide counter on it.
At the beginning of your upkeep, put a tide counter on Tidal Influence.
As long as there is exactly one tide counter on Tidal Influence, all blue creatures get -2/-0.
As long as there are exactly three tide counters on Tidal Influence, all blue creatures get +2/+0.
Whenever there are four or more tide counters on Tidal Influence, remove all tide counters from it.

Sentinel of the Pearl Trident

Flash
When Sentinel of the Pearl Trident enters, you may exile target historic permanent you control. If you do, return that card to the battlefield under its owner's control at the beginning of the next end step. (Artifacts, legendaries, and Sagas are historic.)

Benthic Explorers

{T}, Untap a tapped land an opponent controls: Add one mana of any type that land could produce.

Siren's Call

Cast this spell only during an opponent's turn, before attackers are declared.
Creatures the active player controls attack this turn if able.
At the beginning of the next end step, destroy all non-Wall creatures that player controls that didn't attack this turn. Ignore this effect for each creature the player didn't control continuously since the beginning of the turn.

Triton Shorethief

Interdict

Counter target activated ability from an artifact, creature, enchantment, or land. That permanent's activated abilities can't be activated this turn. (Mana abilities can't be targeted.)
Draw a card.

Deepwater Hypnotist

Inspired — Whenever Deepwater Hypnotist becomes untapped, target creature an opponent controls gets -3/-0 until end of turn.

Shoreline Raider

Dive Down

Target creature you control gets +0/+3 and gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Nyxborn Triton

Bestow {4}{U} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Enchanted creature gets +2/+3.

Words of Wind

{1}: The next time you would draw a card this turn, each player returns a permanent they control to its owner's hand instead.

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.

Scroll Thief

Whenever Scroll Thief deals combat damage to a player, draw a card.

Chain of Vapor

Return target nonland permanent to its owner's hand. Then that permanent's controller may sacrifice a land. If the player does, they may copy this spell and may choose a new target for that copy.

Trickery Charm

Choose one —
• Target creature gains flying until end of turn.
• Target creature becomes the creature type of your choice until end of turn.
• Look at the top four cards of your library, then put them back in any order.

Counterspell

Arcane Signet

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

Standardize

Choose a creature type other than Wall. Each creature becomes that type until end of turn.

Merfolk Looter

Sea Scryer

Enervate

Tap target artifact, creature, or land.
Draw a card at the beginning of the next turn's upkeep.

Arcane Melee

Instant and sorcery spells cost {2} less to cast.

Kraken Hatchling

Mana Chains

Enchant creature
Enchanted creature has "Cumulative upkeep {1}." (At the beginning of its controller's upkeep, that player puts an age counter on it, then sacrifices it unless they pay its upkeep cost for each age counter on it.)

Whelming Wave

Return all creatures to their owners' hands except for Krakens, Leviathans, Octopuses, and Serpents.

Master of Waves

Protection from red
Elemental creatures you control get +1/+1.
When Master of Waves 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.)

Castle Vantress

Castle Vantress enters tapped unless you control an Island.
{T}: Add {U}.
{2}{U}{U}, {T}: Scry 2.

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.

Sea's Claim

Enchant land (Target a land as you cast this. This card enters attached to that land.)
Enchanted land is an Island.

Silvergill Douser

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

Thassa's Bounty

Draw three cards. Target player mills three cards.

Remote Isle

Remote Isle enters tapped.
{T}: Add {U}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Cowardice

Whenever a creature becomes the target of a spell or ability, return that creature to its owner's hand. (It won't be affected by the spell or ability.)

Man-o'-War

When Man-o'-War enters, return target creature to its owner's hand.

Encrust

Enchant artifact or creature
Enchanted permanent doesn't untap during its controller's untap step and its activated abilities can't be activated.

Startling Development

Until end of turn, target creature becomes a blue Serpent with base power and toughness 4/4.
Cycling {1} ({1}, Discard this card: Draw a card.)

Sol Ring

Balance of Power

If target opponent has more cards in hand than you, draw cards equal to the difference.

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, if it was kicked, return all creatures to their owners' hands except for Merfolk, Krakens, Leviathans, Octopuses, and Serpents.

Fortress Crab

Coral Merfolk

Shimmering Wings

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature has flying. (It can't be blocked except by creatures with flying or reach.)
{U}: Return Shimmering Wings to its owner's hand.

Dehydration

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature doesn't untap during its controller's untap step.

Barrin's Unmaking

Return target permanent to its owner's hand if that permanent shares a color with the most common color among all permanents or a color tied for most common.

Evacuation

Return all creatures to their owners' hands.

Vodalian Mage

{U}, {T}: Counter target spell unless its controller pays {1}.

Unsummon

Return target creature to its owner's hand.

Kukemssa Serpent

Kukemssa Serpent can't attack unless defending player controls an Island.
{U}, Sacrifice an Island: Target land an opponent controls becomes an Island until end of turn.
When you control no Islands, sacrifice Kukemssa Serpent.

Boomerang

Return target permanent to its owner's hand.

Dramatic Reversal

Untap all nonland permanents you control.

Mana Short

Tap all lands target player controls and that player loses all unspent mana.

Vodalian Merchant

When Vodalian Merchant enters, draw a card, then discard a card.

Island

Confiscate

Enchant permanent
You control enchanted permanent.

Dissolve

Counter target spell. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Horned Turtle

High Tide

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

Merseine

Enchant creature
Merseine enters with three net counters on it.
Enchanted creature doesn't untap during its controller's untap step if Merseine has a net counter on it.
Pay enchanted creature's mana cost: Remove a net counter from Merseine. Only the controller of the enchanted creature may activate this ability.

Pirate's Prize

Draw two cards. Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Befuddle

Target creature gets -4/-0 until end of turn.
Draw a card.

Floodtide Serpent

Floodtide Serpent can't attack unless you return an enchantment you control to its owner's hand. (This cost is paid as attackers are declared.)

Tidal Wave

Create a 5/5 blue Wall creature token with defender. Sacrifice it at the beginning of the next end step.

Voyage's End

Return target creature to its owner's hand. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Harbor Serpent

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Harbor Serpent can't attack unless there are five or more Islands on the battlefield.

Mystic Sanctuary

({T}: Add {U}.)
Mystic Sanctuary enters tapped unless you control three or more other Islands.
When Mystic Sanctuary enters untapped, you may put target instant or sorcery card from your graveyard on top of your library.