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

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

{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.

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.

{T}: Add {G}.

Channel -- {1}{G}, Discard Boseiju, Who Endures: Destroy target artifact, enchantment, or nonbasic land an opponent controls. That player may search their library for a land card with a basic land type, put it onto the battlefield, then shuffle. This ability costs {1} less to activate for each legendary creature you control.

({T}: Add {G} or {U}.)

As Breeding Pool enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

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

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

Whenever Cold-Eyed Selkie deals combat damage to a player, you may draw that many cards.

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

Whenever an opponent shuffles their library, you may put a +1/+1 counter on Cosi's Trickster.

Counter target spell.

Creatures you control have "{T}: Add one mana of any color."

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

Blue creatures you control can't be blocked.

Whenever another Merfolk enters the battlefield under your control, put a +1/+1 counter on target Merfolk you control.

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.)

Tap an untapped creature you control: Untap target basic land.

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.

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

If you control a commander, you may cast this spell without paying its mana cost.

Counter target noncreature spell.

Search your library and/or graveyard for a creature card with mana value X or less and put it onto the battlefield. If you search your library this way, shuffle. If X is 10 or more, creatures you control get +X/+X and gain haste until end of turn.

{T}, Pay 1 life, Sacrifice Flooded Strand: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

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.

Whenever a nontoken creature enters the battlefield under your control, if it doesn't have the same name as another creature you control or a creature card in your graveyard, draw a card.

Creatures you control with +1/+1 counters on them can't be blocked.

Permanents you control gain hexproof and indestructible until end of turn.

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

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({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.

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)

Destroy target artifact or enchantment.

Kumena's Speaker gets +1/+1 as long as you control another Merfolk or an Island.

Tap another untapped Merfolk you control: Kumena, Tyrant of Orazca can't be blocked this turn.

Tap three untapped Merfolk you control: Draw a card.

Tap five untapped Merfolk you control: Put a +1/+1 counter on each Merfolk you control.

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

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.

Counter target spell. At the beginning of your next main phase, add an amount of {C} equal to that spell's mana value.

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

Other Merfolk you control get +1/+1.

Flying

When Merfolk Skydiver enters the battlefield, put a +1/+1 counter on target creature you control.

{3}{G}{U}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

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

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

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

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

Whenever you cast a Merfolk spell, you may tap or untap target permanent.

As Metallic Mimic enters the battlefield, choose a creature type.

Metallic Mimic is the chosen type in addition to its other types.

Each other creature you control of the chosen type enters the battlefield with an additional +1/+1 counter on it.

Mist-Cloaked Herald can't be blocked.

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

{T}, Pay 1 life, Sacrifice Misty Rainforest: Search your library for a Forest or Island card, put it onto the battlefield, then shuffle.

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

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

Untap all green and/or blue creatures you control during each other player's untap step.

Destroy target artifact or enchantment. Its controller gains 4 life.

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

Counter target noncreature spell.

Counter target spell.

At the beginning of your next upkeep, pay {3}{U}{U}. If you don't, you lose the game.

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

Return all cards from your graveyard to your hand. Exile Praetor's Counsel. You have no maximum hand size for the rest of the game.

{T}, Pay 1 life, Sacrifice Prismatic Vista: Search your library for a basic land card, put it onto the battlefield, then shuffle.

Search your library for a basic land card, put it on the battlefield, then shuffle. Until end of turn, that land becomes a 4/3 Insect creature with reach and haste. It's still a land.

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

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.)

Changeling (This card is every creature type.)

As Realmwalker enters the battlefield, choose a creature type.

You may look at the top card of your library any time.

You may cast creature spells of the chosen type from the top of your library.

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.)

Return target card from your graveyard to your hand.

Rejuvenating Springs enters the battlefield tapped unless you have two or more opponents.

{T}: Add {G} or {U}.

You have no maximum hand size.

{T}: Add {C}.

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

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

{1}, {T}: Tap target land.

River Sneak can't be blocked.

Whenever another Merfolk enters the battlefield under your control, River Sneak gets +1/+1 until end of turn.

Whenever equipped creature deals combat damage to a player, you draw that many cards.

Equip {4}

Equip Shaman, Warlock, or Wizard {1}

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

Untap all permanents you control during each other player's untap step.

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {G}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

{T}: Add {C}{C}.

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.

{T}: Add {C}.

{T}, Sacrifice Strip Mine: Destroy target land.

At the beginning of your draw step, you may draw two additional cards. If you do, choose two cards in your hand drawn this turn. For each of those cards, pay 4 life or put the card on top of your library.

Landfall -- Whenever a land enters the battlefield under your control, you gain 1 life and draw a card.

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.

You have no maximum hand size.

{T}: Add {C}.

{4}: Scry 1, then reveal the top card of your library. If it's a land card, put it onto the battlefield tapped. Otherwise, draw a card.

Partner (You can have two commanders if both have partner.)

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

({T}: Add {G} or {U}.)

Flash

Other Merfolk you control get +1/+1.

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

{T}: Add {C}.

{T}, Sacrifice Wasteland: Destroy target nonbasic land.

{T}, Pay 1 life, Sacrifice Windswept Heath: Search your library for a Forest or Plains card, put it onto the battlefield, then shuffle.

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Each land is a Forest in addition to its other land types.