At the beginning of your upkeep, you may put a charge counter on Aether Vial.

{T}: You may put a creature card with mana value equal to the number of charge counters on Aether Vial from your hand onto the battlefield.

{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.

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

({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.

As Cavern of Souls enters the battlefield, choose a creature type.

{T}: Add {C}.

{T}: Add one mana of any color. Spend this mana only to cast a creature spell of the chosen type, and that spell can't be countered.

When Cenote Scout enters the battlefield, it 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 this creature, then put the card back or put it into your graveyard.)

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.

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

Counter target spell.

Enchant creature

Enchanted creature gets +1/+1 and has "Whenever this creature deals combat damage to a player, you may draw a card."

At the beginning of your end step, if you didn't attack with a creature this turn, sacrifice Curious Obsession.

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

Choose one --

• Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)

• Counter target noncreature spell unless its controller pays {3}.

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

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.

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

If it's not your turn, you may exile a blue card from your hand rather than pay this spell's mana cost.

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

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.

Counter target spell.

({T}: Add {G}.)

You may return two Islands you control to their owner's hand rather than pay this spell's mana cost.

Draw two cards.

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.

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}.)

Flash

If an opponent would draw a card except the first one they draw in each of their draw steps, instead you create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

({T}: Add {U}.)

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.

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

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

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.

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.

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.

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

{T}: Add {C}.

{1}: Mutavault becomes a 2/2 creature with all creature types until end of turn. It's still a land.

+2: Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")

+1: Target artifact or creature loses all abilities and becomes a green Elk creature with base power and toughness 3/3.

-5: Exchange control of target artifact or creature you control and target creature an opponent controls with power 3 or less.

{T}: Add {U}.

Channel -- {3}{U}, Discard Otawara, Soaring City: Return target artifact, creature, enchantment, or planeswalker to its owner's hand. This ability costs {1} less to activate for each legendary creature you control.

You may have Phantasmal Image enter the battlefield as a copy of any creature on the battlefield, except it's an Illusion in addition to its other types and it has "When this creature becomes the target of a spell or ability, sacrifice it."

{T}, Pay 1 life, Sacrifice Polluted Delta: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

{T}, Pay 1 life, Sacrifice Scalding Tarn: Search your library for an Island or Mountain card, put it onto the battlefield, then shuffle.

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.

Counter target noncreature spell unless its controller pays {2}.

Enchant land

When Spreading Seas enters the battlefield, draw a card.

Enchanted land is an Island.

Flash

Flying

When Subtlety enters the battlefield, choose up to one target creature spell or planeswalker spell. Its owner puts it on the top or bottom of their library.

Evoke--Exile a blue card from your 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}.)

Indestructible

When The One Ring enters the battlefield, if you cast it, you gain protection from everything until your next turn.

At the beginning of your upkeep, you lose 1 life for each burden counter on The One Ring.

{T}: Put a burden counter on The One Ring, then draw a card for each burden counter on The One Ring.

Kicker {1} (You may pay an additional {1} as you cast this spell.)

When Tide Shaper enters the battlefield, if it was kicked, target land becomes an Island for as long as Tide Shaper remains on the battlefield.

Tide Shaper gets +1/+1 as long as an opponent controls an Island.

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.)

Triton Shorestalker can't be blocked.

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

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

True-Name Nemesis has protection from the chosen player.

Return target creature to its owner's hand. Its controller loses 1 life.

Flash

Other Merfolk you control get +1/+1.

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

{T}, Pay 1 life: Add {G} or {U}.

{1}, {T}, Sacrifice Waterlogged Grove: Draw a card.