Merfolk Skyscout

Flying
Whenever Merfolk Skyscout attacks or blocks, untap target permanent.

Augur of Bolas

When Augur of Bolas enters the battlefield, look at the top three cards of your library. You may reveal an instant or sorcery card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Kraken Hatchling

Counterspell

Kraken's Eye

Whenever a player casts a blue spell, you may gain 1 life.

Kraken of the Straits

Creatures with power less than the number of Islands you control can't block Kraken of the Straits.

Wayfarer's Bauble

{2}, {T}, Sacrifice Wayfarer's Bauble: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Treasure Cruise

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Draw three cards.

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.

Polymorphist's Jest

Until end of turn, each creature target player controls loses all abilities and becomes a blue Frog with base power and toughness 1/1.

Nadir Kraken

Whenever you draw a card, you may pay {1}. If you do, put a +1/+1 counter on Nadir Kraken and create a 1/1 blue Tentacle creature token.

Faerie Trickery

Counter target non-Faerie spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Devastation Tide

Return all nonland permanents to their owners' hands.
Miracle {1}{U} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)

Verity Circle

Whenever a creature an opponent controls becomes tapped, if it isn't being declared as an attacker, you may draw a card.
{4}{U}: Tap target creature without flying.

Thought Collapse

Counter target spell. Its controller mills three cards.

Sol Ring

Serum Visions

Sinister Sabotage

Counter target spell.
Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Cryptic Serpent

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

Foil

You may discard an Island card and another card rather than pay this spell's mana cost.
Counter target spell.

Spell Swindle

Counter target spell. Create X Treasure tokens, where X is that spell's mana value. (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Island

Frozen Aether

Artifacts, creatures, and lands your opponents control enter the battlefield tapped.

Karn's Temporal Sundering

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Target player takes an extra turn after this one. Return up to one target nonland permanent to its owner's hand. Exile Karn's Temporal Sundering.

Jace's Sanctum

Instant and sorcery spells you cast cost {1} less to cast.
Whenever you cast an instant or sorcery spell, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Gearseeker Serpent

This spell costs {1} less to cast for each artifact you control.
{5}{U}: Gearseeker Serpent can't be blocked this turn.

Preordain

Scry 2, then draw a card. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

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.

Rapid Hybridization

Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.

Octoprophet

When Octoprophet enters the battlefield, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom of your library and the rest on top in any order.)

Rush of Knowledge

Draw cards equal to the highest mana value among permanents you control.

Propaganda

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Aetherize

Return all attacking creatures to their owner's hand.

Serpent of Yawning Depths

Krakens, Leviathans, Octopuses, and Serpents you control can't be blocked except by Krakens, Leviathans, Octopuses, and Serpents.

Spell Snuff

Counter target spell.
Fateful hour — If you have 5 or less life, draw a card.

Portcullis

Whenever a creature enters the battlefield, if there are two or more other creatures on the battlefield, exile that creature. Return that card to the battlefield under its owner's control when Portcullis leaves the battlefield.

Fact or Fiction

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Halimar Depths

Halimar Depths enters the battlefield tapped.
When Halimar Depths enters the battlefield, look at the top three cards of your library, then put them back in any order.
{T}: Add {U}.

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

Rewind

Counter target spell. Untap up to four lands.

Dissipation Field

Whenever a permanent deals damage to you, return it to its owner's hand.

Sky Diamond

Sky Diamond enters the battlefield tapped.
{T}: Add {U}.

Charix, the Raging Isle

Spells your opponents cast that target Charix, the Raging Isle cost {2} more to cast.
{3}: Charix gets +X/-X until end of turn, where X is the number of Islands you control.

Arcane Signet

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

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Retreat to Coralhelm

Landfall — Whenever a land enters the battlefield under your control, choose one —
• You may tap or untap target creature.
• Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Negate

Merfolk Trickster

Flash
When Merfolk Trickster enters the battlefield, tap target creature an opponent controls. It loses all abilities until end of turn.

Expedition Map

{2}, {T}, Sacrifice Expedition Map: Search your library for a land card, reveal it, put it into your hand, then shuffle.

Thran Dynamo

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

High Tide

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

Bident of Thassa

Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.

Heraldic Banner

As Heraldic Banner enters the battlefield, choose a color.
Creatures you control of the chosen color get +1/+0.
{T}: Add one mana of the chosen color.

Ominous Seas

Whenever you draw a card, put a foreshadow counter on Ominous Seas.
Remove eight foreshadow counters from Ominous Seas: Create an 8/8 blue Kraken creature token.
Cycling {2} ({2}, Discard this card: Draw a card.)

Myriad Landscape

Myriad Landscape enters the battlefield tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Unwind

Counter target noncreature spell. Untap up to three lands.

Worn Powerstone

Worn Powerstone enters the battlefield tapped.
{T}: Add {C}{C}.

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Thassa's Oracle

When Thassa's Oracle enters the battlefield, look at the top X cards of your library, where X is your devotion to blue. Put up to one of them on top of your library and the rest on the bottom of your library in a random order. If X is greater than or equal to the number of cards in your library, you win the game. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Reliquary Tower

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

War Tax

{X}{U}: This turn, creatures can't attack unless their controller pays {X} for each attacking creature they control.