Glint

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.)

Air Marshal

{3}: Target Soldier gains flying until end of turn.

Brine Giant

This spell costs {1} less to cast for each enchantment you control.

Spectral Flight

Enchant creature
Enchanted creature gets +2/+2 and has flying.

Stealth Mission

Put two +1/+1 counters on target creature you control. That creature can't be blocked this turn.

Stonybrook Angler

{1}{U}, {T}: You may tap or untap target creature.

Negate

Deep-Sea Terror

Deep-Sea Terror can't attack unless there are seven or more cards in your graveyard.

Frogify

Enchant creature
Enchanted creature loses all abilities and is a blue Frog creature with base power and toughness 1/1. (It loses all other card types and creature types.)

Eel Umbra

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
Enchanted creature gets +1/+1.
Totem armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Crashing Tide

This spell has flash as long as you control a Merfolk.
Return target creature to its owner's hand.
Draw a card.

Fall from Favor

Enchant creature
When Fall from Favor enters the battlefield, tap enchanted creature and you become the monarch.
Enchanted creature doesn't untap during its controller's untap step unless that player is the monarch.

Cartouche of Knowledge

Enchant creature you control
When Cartouche of Knowledge enters the battlefield, draw a card.
Enchanted creature gets +1/+1 and has flying.

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.

Skaab Goliath

As an additional cost to cast this spell, exile two creature cards from your graveyard.
Trample

Capsizing Wave

Return target creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

Sword Coast Serpent

Sword Coast Serpent can't be blocked as long as you've cast a noncreature spell this turn.

Sword Coast Serpent // Capsizing Wave

Jeskai Windscout

Flying
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Triton Fortune Hunter

Heroic — Whenever you cast a spell that targets Triton Fortune Hunter, draw a card.

Jhessian Thief

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever Jhessian Thief deals combat damage to a player, draw a card.

Artful Dodge

Target creature can't be blocked this turn.
Flashback {U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Island

Shipwreck Dowser

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

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.

Dive Down

Counterspell

Archaeomancer

When Archaeomancer enters the battlefield, return target instant or sorcery card from your graveyard to your hand.

Shaper Apprentice

Shaper Apprentice has flying as long as you control another Merfolk.

Salvager of Secrets

When Salvager of Secrets enters the battlefield, return target instant or sorcery card from your graveyard to your hand.

Wing Commando

Saiba Cryptomancer

Flash
Backup 1 (When this creature enters the battlefield, put a +1/+1 counter on target creature. If that's another creature, it gains the following ability until end of turn.)
Hexproof

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.

One With the Wind

Ghostly Wings

Enchant creature
Enchanted creature gets +1/+1 and has flying.
Discard a card: Return enchanted creature to its owner's hand.

Hubris

Return target creature and all Auras attached to it to their owners' hands.

Viscerid Armor

Enchant creature
Enchanted creature gets +1/+1.
{1}{U}: Return Viscerid Armor to its owner's hand.

Merfolk Coralsmith

{1}: Merfolk Coralsmith gets +1/-1 until end of turn.
When Merfolk Coralsmith dies, scry 2.

Starlit Mantle

Flash
Enchant creature you control
When Starlit Mantle enters the battlefield, enchanted creature gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
Enchanted creature gets +1/+1.

Niblis of Dusk

Whirlwind Adept

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Riverwheel Aerialists

Dispel

Defy Gravity

Target creature gains flying until end of turn.
Flashback {U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

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.

Cerulean Wisps

Target creature becomes blue until end of turn. Untap that creature.
Draw a card.

Goliath Sphinx

Aqueous Form

Enchant creature
Enchanted creature can't be blocked.
Whenever enchanted creature attacks, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Arcane Signet

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

Mistral Singer

High Tide

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

Arcane Flight

Enchant creature
Enchanted creature gets +1/+1 and has flying.

Leap

Target creature gains flying until end of turn.
Draw a card.

Cryptic Serpent

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.

Mnemonic Wall

Defender
When Mnemonic Wall enters the battlefield, you may return target instant or sorcery card from your graveyard to your hand.

Cradle of Safety

Flash
Enchant creature you control
When Cradle of Safety enters the battlefield, enchanted creature gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
Enchanted creature gets +1/+1.

Mystic Sanctuary

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

Marauding Brinefang

Ward {3} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
Islandcycling {2} ({2}, Discard this card: Search your library for an Island card, reveal it, put it into your hand, then shuffle.)

Bubble Up

Put target instant or sorcery card from your graveyard on top of your library. (Then exile this card. You may cast the creature later from exile.)

Aquatic Alchemist

Whenever you cast your first instant or sorcery spell each turn, Aquatic Alchemist gets +2/+0 until end of turn.

Aquatic Alchemist // Bubble Up

Silvergill Douser

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

Expanded Anatomy

Put two +1/+1 counters on target creature. It gains vigilance until end of turn.

Water Wings

Until end of turn, target creature you control has base power and toughness 4/4 and gains flying and hexproof. (It can't be the target of spells or abilities your opponents control.)

Gray Harbor Merfolk

Gray Harbor Merfolk can't be blocked.
Gray Harbor Merfolk gets +2/+0 as long as you control a commander that's a creature or planeswalker.

Ingenious Skaab

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
{U}: Ingenious Skaab gets +1/-1 until end of turn.

Faerie Seer

Flying
When Faerie Seer enters the battlefield, scry 2.

Striped Riverwinder

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Cycling {U} ({U}, Discard this card: Draw a card.)