Silent Departure

Return target creature to its owner's hand.
Flashback {4}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Shipwreck Dowser

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
When this creature enters, return target instant or sorcery card from your graveyard to your hand.

Keep Out

Choose one —
• Keep Out deals 4 damage to target tapped creature.
• Destroy target enchantment.

Blossombind

Enchant creature
When this Aura enters, tap enchanted creature.
Enchanted creature can't become untapped and can't have counters put on it.

Wanderbrine Trapper

{1}, {T}, Tap another untapped creature you control: Tap target creature an opponent controls.

Shore Lurker

Flying
When this creature enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Deep Analysis

Target player draws two cards.
Flashback—{1}{U}, Pay 3 life. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Return to Dust

Exile target artifact or enchantment. If you cast this spell during your main phase, you may exile up to one other target artifact or enchantment.

Merrow Skyswimmer

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Flying, vigilance
When this creature enters, create a 1/1 white and blue Merfolk creature token.

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.

Ajani's Pridemate

Whenever you gain life, put a +1/+1 counter on this creature.

Mocking Sprite

Flying
Instant and sorcery spells you cast cost {1} less to cast.

Wanderbrine Preacher

Whenever this creature becomes tapped, you gain 2 life.

Mist Raven

Flying
When this creature enters, return target creature to its owner's hand.

Millstone

Jace, Unraveler of Secrets

+1: Scry 1, then draw a card.
−2: Return target creature to its owner's hand.
−8: You get an emblem with "Whenever an opponent casts their first spell each turn, counter that spell."

Summit Sentinel

Wistfulness

When this creature enters, if {G}{G} was spent to cast it, exile target artifact or enchantment an opponent controls.
When this creature enters, if {U}{U} was spent to cast it, draw two cards, then discard a card.
Evoke {G/U}{G/U} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Gravelgill Scoundrel

Vigilance
Whenever this creature attacks, you may tap another untapped creature you control. If you do, this creature can't be blocked this turn.

Serum Visionary

When this creature enters, draw a card, then scry 2.

Wanderwine Distracter

Whenever this creature becomes tapped, target creature an opponent controls gets -3/-0 until end of turn.

Serra Angel

Flying
Vigilance (Attacking doesn't cause this creature to tap.)

Plains

Niblis of the Urn

Flying
Whenever this creature attacks, you may tap target creature.

Blink of an Eye

Kicker {1}{U} (You may pay an additional {1}{U} as you cast this spell.)
Return target nonland permanent to its owner's hand. If this spell was kicked, draw a card.

Refute

Counter target spell. Draw a card, then discard a card.

Deepchannel Duelist

At the beginning of your end step, untap target Merfolk you control.
Other Merfolk you control get +1/+1.

Island

Glamermite

Flash
Flying
When this creature enters, choose one —
• Tap target creature.
• Untap target creature.

Sygg's Command

Choose two —
• Create a token that's a copy of target Merfolk you control.
• Creatures target player controls gain lifelink until end of turn.
• Target player draws a card.
• Tap target creature. Put a stun counter on it.

Stuck in Summoner's Sanctum

Flash
Enchant artifact or creature
When this Aura enters, tap enchanted permanent.
Enchanted permanent doesn't untap during its controller's untap step and its activated abilities can't be activated.

Inspiration from Beyond

Mill three cards, then return an instant or sorcery card from your graveyard to your hand.
Flashback {5}{U}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Tributary Vaulter

Flying
Whenever this creature becomes tapped, another target Merfolk you control gets +2/+0 until end of turn.