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.

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

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.

Castle Vantress enters the battlefield tapped unless you control an Island.

{T}: Add {U}.

{2}{U}{U}, {T}: Scry 2.

Whenever a creature you control deals combat damage to an opponent, you may draw a card.

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

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.

Counter target spell.

Sacrifice Cursecatcher: Counter target instant or sorcery spell unless its controller pays {1}.

Whenever one or more nontoken Merfolk you control become tapped, create a 1/1 blue Merfolk creature token with hexproof.

Whenever you cast a Merfolk spell, create a 1/1 blue Merfolk creature token with hexproof. (A creature with hexproof can't be the target of spells or abilities your opponents control.)

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

Look at the top seven cards of your library. Put two of them into your hand and the rest on the bottom of your library in any order.

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead.

If an effect would put one or more counters on a permanent you control, it puts twice that many of those counters on that permanent instead.

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.

Council's dilemma -- Starting with you, each player votes for time or money. For each time vote, take an extra turn after this one. For each money vote, choose a permanent owned by the voter and gain control of it. Exile Expropriate.

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

When Forerunner of the Heralds enters the battlefield, you may search your library for a Merfolk card, reveal it, then shuffle and put that card on top.

Whenever another Merfolk enters the battlefield under your control, put a +1/+1 counter on Forerunner of the Heralds.

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

Play with the top card of your library revealed.

You may play lands and cast spells from the top of your library.

At the beginning of combat on your turn, each Merfolk creature you control explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on the exploring creature, then put the card back or put it into your graveyard.)

Whenever Hakbal of the Surging Soul attacks, you may put a land card from your hand onto the battlefield. If you don't, draw a card.

You may cast Harbinger of the Tides as though it had flash if you pay {2} more to cast it. (You may cast it any time you could cast an instant.)

When Harbinger of the Tides enters the battlefield, you may return target tapped creature an opponent controls to its owner's hand.

If one or more +1/+1 counters would be put on a creature you control, that many plus one +1/+1 counters are put on it instead.

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

Imprint -- When Isochron Scepter enters the battlefield, you may exile an instant card with mana value 2 or less from your hand.

{2}, {T}: You may copy the exiled card. If you do, you may cast the copy without paying its mana cost.

Counter target spell unless its controller pays {1}.

Jwari Ruins enters the battlefield tapped.

{T}: Add {U}.

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.

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.

Lonely Sandbar enters the battlefield tapped.

{T}: Add {U}.

Cycling {U} ({U}, Discard this card: Draw a card.)

Whenever a spell or ability you control counters a spell, you may create a 1/1 blue Merfolk creature token.

Tap seven untapped Merfolk you control: Counter target spell.

As an additional cost to cast this spell, you may exile any number of blue cards from your hand. This spell costs {2} less to cast for each card exiled this way.

Up to X target creatures phase out. (While they're phased out, they're treated as though they don't exist. Each one phases in before its controller untaps during their next untap step.)

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

Search your library for a blue instant card, reveal that card, put it into your hand, then shuffle.

Other Merfolk creatures you control get +1/+1.

{T}: Target Merfolk creature can't be blocked this turn.

Flash

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

At the beginning of your end step, untap all Merfolk you control.

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.

Whenever you attack with two or more creatures, draw a card.

{T}: Add {U}.

{U}, {T}: Untap target legendary permanent.

Sacrifice Mistcaller: Until end of turn, if a nontoken creature would enter the battlefield and it wasn't cast, exile it instead.

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.

({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.

Search your library for an instant or sorcery card, reveal it, then shuffle and put that card on top.

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Take an extra turn after this one.

If Nexus of Fate would be put into a graveyard from anywhere, reveal Nexus of Fate and shuffle it into its owner's library instead.

Whenever a creature you control explores a land card, you may put a land card from your hand onto the battlefield tapped.

Whenever a creature you control explores a nonland card, put a +1/+1 counter on Nicanzil, Current Conductor.

{T}: Add {C}.

{2}, {T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Path of Ancestry enters the battlefield tapped.

{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)

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

Cycling {2} ({2}, Discard this card: Draw a card.)

Remote Isle enters the battlefield tapped.

{T}: Add {U}.

Cycling {2} ({2}, Discard this card: Draw a card.)

Exile target artifact or creature. Its controller creates a 4/4 blue and red Elemental creature token.

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

{T}: Add {C}.

{4}, {T}: Target creature can't be blocked this turn.

{T}: Add {C}.

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

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

{3}, {T}: Search your library for a Merfolk permanent card, put it onto the battlefield, then shuffle.

Look at the top six 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 a random order.

Silundi Isle enters the battlefield tapped.

{T}: Add {U}.

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.

Flash

When Singer of Swift Rivers enters the battlefield, put a shield counter on another target creature you control. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

You may cast Merfolk spells as though they had flash.

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}: Add {C}{C}.

Enchant land

When Spreading Seas enters the battlefield, draw a card.

Enchanted land is an Island.

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.

Whenever Surgespanner becomes tapped, you may pay {1}{U}. If you do, return target permanent to its owner's hand.

Svyelun of Sea and Sky has indestructible as long as you control at least two other Merfolk.

Whenever Svyelun attacks, draw a card.

Other Merfolk you control have ward {1}. (Whenever another Merfolk you control becomes the target of a spell or ability an opponent controls, counter it unless that player pays {1}.)

{T}: Add {C}.

{T}: Add {G} or {U}. Talisman of Curiosity deals 1 damage to you.

When Tempest Caller enters the battlefield, tap all creatures target opponent controls.

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

Take an extra turn after this one. Exile Temporal Trespass.

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Whenever Thada Adel, Acquisitor deals combat damage to a player, search that player's library for an artifact card and exile it. Then that player shuffles. Until end of turn, you may play that card.

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.)

Kicker {X}. X can't be 0. (You may pay an additional {X} as you cast this spell.)

Flying

When Thieving Skydiver enters the battlefield, if it was kicked, gain control of target artifact with mana value X or less. If that artifact is an Equipment, attach it to Thieving Skydiver.

Search your library for a Forest card, put it onto the battlefield, then shuffle.

Flash

When Tishana's Tidebinder enters the battlefield, counter up to one target activated or triggered ability. If an ability of an artifact, creature, or planeswalker is countered this way, that permanent loses all abilities for as long as Tishana's Tidebinder remains on the battlefield. (Mana abilities can't be targeted.)

When Topography Tracker enters the battlefield, create a Map token. (It's an artifact with "{1}, {T}, Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery.")

If a creature you control would explore, instead it explores, then it explores again.

As True-Name Nemesis enters the battlefield, choose a player.

True-Name Nemesis has protection from the chosen player.

{T}: Add {C}.

{2}, {T}: Target legendary creature becomes a God in addition to its other types. Put a +1/+1 counter on it.

{4}, {T}, Sacrifice Tyrite Sanctum: Put an indestructible counter on target God.

Flash

Other Merfolk you control get +1/+1.

Sacrifice a Merfolk: Counter target noncreature spell unless its controller pays {1}.

{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.)

Champion a Merfolk (When this enters the battlefield, sacrifice it unless you exile another Merfolk you control. When this leaves the battlefield, that card returns to the battlefield.)

Whenever Wanderwine Prophets deals combat damage to a player, you may sacrifice a Merfolk. If you do, take an extra turn after this one.

Return each creature without a +1/+1 counter on it to its owner's hand.