Flash Ward {2} Probing Telepathy — Whenever a creature entering the battlefield under an opponent's control causes a triggered ability of that creature to trigger, you may copy that ability. You may choose new targets for the copy.

{1}{U}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.) Whenever one or more +1/+1 counters are put on Benthic Biomancer, draw a card, then discard a card.

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

Whenever Cephalid Illusionist becomes the target of a spell or ability, mill three cards. {2}{U}, {T}: Prevent all combat damage that would be dealt to and dealt by target creature you control this turn.

Whenever you draw a card, put a +1/+1 counter on Chasm Skulker. When Chasm Skulker dies, create X 1/1 blue Squid creature tokens with islandwalk, where X is the number of +1/+1 counters on Chasm Skulker. (They can't be blocked as long as defending player controls an Island.)

{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.

Blue creatures you control can't be blocked.

You may look at the top card of your library any time. You may cast Merfolk spells from the top of your library. Whenever you cast a Merfolk spell, you may pay {1}. If you do, create a 1/1 blue Merfolk creature token.

Other Merfolk get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

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

{T}: Draw a card, then discard a card.

{T}: Switch target creature's power and toughness until end of turn.

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

Islandwalk (This creature can't be blocked as long as defending player controls an Island.) When Merrow Harbinger enters the battlefield, you may search your library for a Merfolk card, reveal it, then shuffle and put that card on top.

Other Merfolk creatures you control get +1/+1. Whenever you cast a Merfolk spell, you may tap or untap target permanent.

When Mesmerizing Benthid enters the battlefield, create two 0/2 blue Illusion creature tokens with "Whenever this creature blocks a creature, that creature doesn't untap during its controller's next untap step." Mesmerizing Benthid has hexproof as long as you control an Illusion.

This spell can't be countered. You have no maximum hand size. Whenever an opponent casts a noncreature spell, draw a card. Discard three cards: Exile Nezahal, Primal Tide. Return it to the battlefield tapped under its owner's control at the beginning of the next end step.

When Purple-Crystal Crab dies, draw a card.

{T}: Gain control of target creature for as long as that creature is enchanted.

Each other Wizard creature you control enters the battlefield with an additional +1/+1 counter on it. {2}, Remove a +1/+1 counter from a creature you control: Draw a card.

When Scourge of Fleets enters the battlefield, return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.

{T}: Add {C}. {1}, {T}: Add {U}.

Mutate {1}{U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Flash Whenever this creature deals combat damage to a player, draw a card.

Whenever a Merfolk you control deals combat damage to a player, draw a card.

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.

As an additional cost to cast this spell, reveal a Merfolk card from your hand or pay {3}. When Silvergill Adept enters the battlefield, draw a card.

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.

{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.

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.)

Any player may cast spells as though they had flash. Your opponents can't cast spells during your turn.

{T}: Add {C}. Spend this mana only to cast an instant or sorcery spell.

{U}{U}, {T}: Target creature phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before its controller untaps during their next untap step.)

Exile a creature card from your graveyard and pay its mana cost: Create a token that's a copy of that card. Activate only as a sorcery.

Enchant permanent You control enchanted permanent.

{1}, Sacrifice a land: Draw a card. Any player may activate this ability.

Enchant creature When enchanted creature dies, return that card to the battlefield under your control.

As Kindred Discovery enters the battlefield, choose a creature type. Whenever a creature you control of the chosen type enters the battlefield or attacks, draw a card.

Enchant creature Merseine enters the battlefield 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.

Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.) Whenever an opponent casts a noncreature spell, you may draw a card unless that player pays {4}.

At the beginning of your upkeep, sacrifice Sunken City unless you pay {U}{U}. Blue creatures get +1/+1.

Enchant creature When Tangle Kelp enters the battlefield, tap enchanted creature. Enchanted creature doesn't untap during its controller's untap step if it attacked during its controller's last turn.

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.)

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

Counter target spell. Clash with an opponent. If you win, at the beginning of your next main phase, you may add an amount of {C} equal to that spell's mana value. (Each clashing player reveals the top card of their library, then puts that card on the top or bottom. A player wins if their card had a higher mana value.)

Coral Atoll enters the battlefield tapped. When Coral Atoll enters the battlefield, sacrifice it unless you return an untapped Island you control to its owner's hand. {T}: Add {C}{U}.

If you control two or more other lands, Hall of Storm Giants enters the battlefield tapped. {T}: Add {U}. {5}{U}: Until end of turn, Hall of Storm Giants becomes a 7/7 blue Giant creature with ward {3}. It's still a land. (Whenever it becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)

({T}: Add {U}.)

Put a flood counter on target land. That land is an Island in addition to its other types for as long as it has a flood counter on it. If you control a Merfolk, draw a card.

Return target creature and target land to their owners' hands.

Surge {3}{U}{U} (You may cast this spell for its surge cost if you or a teammate has cast another spell this turn.) Return all nonland permanents to their owners' hands. If this spell's surge cost was paid, create an 8/8 blue Octopus creature token.

Reveal cards from the top of your library until you reveal three nonland cards. Put the nonland cards revealed this way into your hand, then put the rest of the revealed cards on the bottom of your library in any order.

Draw X cards, where X is the number of card types among cards in your graveyard.

Draw X cards.

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

Draw a card. Clash with an opponent. If you win, return Research the Deep to its owner's hand. (Each clashing player reveals the top card of their library, then puts that card on the top or bottom. A player wins if their card had a higher mana value.)

Put target creature on top of its owner's library.