Twiddle

You may tap or untap target artifact, creature, or land.

High Tide

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

Ludevic's Abomination

Ludevic's Test Subject

Defender
{1}{U}: Put a hatchling counter on Ludevic's Test Subject. Then if there are five or more hatchling counters on it, remove all of them and transform it.

Ludevic's Test Subject // Ludevic's Abomination

Disperse

Return target nonland permanent to its owner's hand.

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.

Counterspell

Dakra Mystic

{U}, {T}: Each player reveals the top card of their library. You may put the revealed cards into their owners' graveyards. If you don't, each player draws a card.

Entrancing Melody

Gain control of target creature with mana value X.

Aether Gust

Choose target spell or permanent that's red or green. Its owner puts it on the top or bottom of their library.

Merfolk Looter

Selective Snare

Return X target creatures of the creature type of your choice to their owner's hand.

Cancel

Sensory Deprivation

Enchant creature
Enchanted creature gets -3/-0.

Fog Bank

Defender, flying
Prevent all combat damage that would be dealt to and dealt by Fog Bank.

Swarm Intelligence

Whenever you cast an instant or sorcery spell, you may copy that spell. You may choose new targets for the copy.

Ghostform

Up to two target creatures can't be blocked this turn.

Unsummon

Return target creature to its owner's hand.

Island

Merfolk Spy

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Merfolk Spy deals combat damage to a player, that player reveals a card at random from their hand.

Essence Scatter

Caller of Gales

{1}{U}, {T}: Target creature gains flying until end of turn.

Wall of Air

Defender, flying (This creature can't attack, and it can block creatures with flying.)

Desertion

Counter target spell. If an artifact or creature spell is countered this way, put that card onto the battlefield under your control instead of into its owner's graveyard.

Peel from Reality

Return target creature you control and target creature you don't control to their owners' hands.

Frost Breath

Tap up to two target creatures. Those creatures don't untap during their controller's next untap step.

Ray of Command

Untap target creature an opponent controls and gain control of it until end of turn. That creature gains haste until end of turn. When you lose control of the creature, tap it.

Syncopate

Counter target spell unless its controller pays {X}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

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.

Peregrine Drake

Flying
When Peregrine Drake enters the battlefield, untap up to five lands.

Vault Skyward

Target creature gains flying until end of turn. Untap it.

Diminish

Target creature has base power and toughness 1/1 until end of turn.

Mist-Cloaked Herald

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.

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.

Maritime Guard

Merfolk of the Pearl Trident

Watertrap Weaver

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

Quasiduplicate

Create a token that's a copy of target creature you control.
Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)

Sentinel of the Pearl Trident

Flash
When Sentinel of the Pearl Trident enters the battlefield, 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.)