Look at the top three cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.
{3}{U}
Aquatic Incursion
Enchantment
When Aquatic Incursion enters the battlefield, create two 1/1 blue Merfolk creature tokens with hexproof. (They can't be the targets of spells or abilities your opponents control.)
{3}{U}: Target Merfolk can't be blocked this turn.
{1}{U}
Augur of Bolas
Creature - Merfolk Wizard
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.
1 /
3
--
Bant Panorama
Land
{T}: Add {C}.
{1}, {T}, Sacrifice Bant Panorama: Search your library for a basic Forest, Plains, or Island card, put it onto the battlefield tapped, then shuffle.
{2}{G}
Beast Within
Instant
Destroy target permanent. Its controller creates a 3/3 green Beast creature token.
{1}{G}
Bonds of Mortality
Enchantment
When Bonds of Mortality enters the battlefield, draw a card.
{G}: Creatures your opponents control lose hexproof and indestructible until end of turn.
{U}
Brainstorm
Instant
Draw three cards, then put two cards from your hand on top of your library in any order.
{1}{U}{U}
Cackling Counterpart
Instant
Create a token that's a copy of target creature you control.
Flashback {5}{U}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)
{1}{G/U}{G/U}
Cold-Eyed Selkie
Creature - Merfolk Rogue
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.
1 /
1
--
Command Tower
Land
{T}: Add one mana of any color in your commander's color identity.
{3}
Commander's Sphere
Artifact
{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.
{U}{U}
Counterspell
Instant
Counter target spell.
{1}{G}
Cryptolith Rite
Enchantment
Creatures you control have "{T}: Add one mana of any color."
{2}{G}
Cultivate
Sorcery
Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.
{2}{U}
Deeproot Waters
Enchantment
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.)
{U}
Dispel
Instant
Counter target instant spell.
{1}{U}{U}
Dissipate
Instant
Counter target spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.
{1}{U}{U}
Dissolve
Instant
Counter target spell. Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)
--
Evolving Wilds
Land
{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{2}
Fellwar Stone
Artifact
{T}: Add one mana of any color that a land an opponent controls could produce.
{3}{G}
Forerunner of the Heralds
Creature - Merfolk Scout
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.
3 /
2
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
--
Forest
Basic Land - Forest
({T}: Add {G}.)
{U}{U}
Harbinger of the Tides
Creature - Merfolk Wizard
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.
2 /
2
{3}{U}
Herald of Secret Streams
Creature - Merfolk Warrior
Creatures you control with +1/+1 counters on them can't be blocked.
2 /
3
--
Hinterland Harbor
Land
Hinterland Harbor enters the battlefield tapped unless you control a Forest or an Island.
{T}: Add {G} or {U}.
{1}{U}
Impulse
Instant
Look at the top four cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.
{1}{U}
Ink Dissolver
Creature - Merfolk Wizard
Kinship -- At the beginning of your upkeep, you may look at the top card of your library. If it shares a creature type with Ink Dissolver, you may reveal it. If you do, each opponent mills three cards.
2 /
1
{1}{U}
Into the Roil
Instant
Kicker {1}{U} (You may pay an additional {1}{U} as you cast this spell.)
Return target nonland permanent to its owner's hand. If this spell was kicked, draw a card.
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
--
Island
Basic Land - Island
({T}: Add {U}.)
{2}{G}
Jungleborn Pioneer
Creature - Merfolk Scout
When Jungleborn Pioneer enters the battlefield, create a 1/1 blue Merfolk creature token with hexproof. (It can't be the target of spells or abilities your opponents control.)
2 /
2
{G}{U}
Kiora's Follower
Creature - Merfolk
{T}: Untap another target permanent.
2 /
2
{1}{U}{U}
Kopala, Warden of Waves
Legendary Creature - Merfolk Wizard
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.
2 /
2
{2}{G}
Krosan Grip
Instant
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.
{2}{U}{U}
Kumena's Awakening
Enchantment
Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
At the beginning of your upkeep, each player draws a card. If you have the city's blessing, instead only you draw a card.
{G}
Kumena's Speaker
Creature - Merfolk Shaman
Kumena's Speaker gets +1/+1 as long as you control another Merfolk or an Island.
1 /
1
{1}{G}{U}
Kumena, Tyrant of Orazca
Legendary Creature - Merfolk Shaman
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.
2 /
4
{3}
Lifecrafter's Bestiary
Artifact
At the beginning of your upkeep, scry 1.
Whenever you cast a creature spell, you may pay {G}. If you do, draw a card.
{1}{U}{U}
Lullmage Mentor
Creature - Merfolk Wizard
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.
2 /
2
{1}{U}
Mana Leak
Instant
Counter target spell unless its controller pays {3}.
{G}{U}
Merfolk Mistbinder
Creature - Merfolk Shaman
Other Merfolk you control get +1/+1.
2 /
2
{1}{U}{U}
Merfolk Sovereign
Creature - Merfolk Noble
Other Merfolk creatures you control get +1/+1.
{T}: Target Merfolk creature can't be blocked this turn.
2 /
2
{U}{U}
Merfolk Trickster
Creature - Merfolk Wizard
Flash
When Merfolk Trickster enters the battlefield, tap target creature an opponent controls. It loses all abilities until end of turn.
2 /
2
{2}{U}
Mirror Image
Creature - Shapeshifter
You may have Mirror Image enter the battlefield as a copy of a creature you control.
0 /
0
{U}
Mizzium Skin
Instant
Target creature you control gets +0/+1 and gains hexproof until end of turn.
Overload {1}{U} (You may cast this spell for its overload cost. If you do, change its text by replacing all instances of "target" with "each.")
{2}{G/U}{G/U}{G/U}
Murkfiend Liege
Creature - Horror
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.
4 /
4
{3}{U}{U}
Mystic Confluence
Instant
Choose three. You may choose the same mode more than once.
• Counter target spell unless its controller pays {3}.
• Return target creature to its owner's hand.
• Draw a card.
{U}
Mystic Remora
Enchantment
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}.
{1}{G}
Naturalize
Instant
Destroy target artifact or enchantment.
{1}{U}
Negate
Instant
Counter target noncreature spell.
{U}
Opt
Instant
Scry 1.
Draw a card.
{2}{G}{G}{G}
Overrun
Sorcery
Creatures you control get +3/+3 and gain trample until end of turn.
{3}{G}{G}
Overwhelming Stampede
Sorcery
Until end of turn, creatures you control gain trample and get +X/+X, where X is the greatest power among creatures you control.
{3}{G}
Path of Discovery
Enchantment
Whenever a creature enters the battlefield under your control, 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 the creature, then put the card back or put it into your graveyard.)
{1}{G}
Rampant Growth
Sorcery
Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
{1}{G}
Regrowth
Sorcery
Return target card from your graveyard to your hand.
--
Remote Isle
Land
Remote Isle enters the battlefield tapped.
{T}: Add {U}.
Cycling {2} ({2}, Discard this card: Draw a card.)
{1}{U}
Shaper Apprentice
Creature - Merfolk Wizard
Shaper Apprentice has flying as long as you control another Merfolk.
2 /
1
{1}{U}
Shapesharer
Creature - Shapeshifter
Changeling (This card is every creature type.)
{2}{U}: Target Shapeshifter becomes a copy of target creature until your next turn.
1 /
1
{1}{U}
Silvergill Adept
Creature - Merfolk Wizard
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.
2 /
1
{G}{U}
Simic Charm
Instant
Choose one --
• Target creature gets +3/+3 until end of turn.
• Permanents you control gain hexproof until end of turn.
• Return target creature to its owner's hand.
{2}
Simic Signet
Artifact
{1}, {T}: Add {G}{U}.
--
Slippery Karst
Land
Slippery Karst enters the battlefield tapped.
{T}: Add {G}.
Cycling {2} ({2}, Discard this card: Draw a card.)
{1}
Sol Ring
Artifact
{T}: Add {C}{C}.
{U}
Spell Pierce
Instant
Counter target noncreature spell unless its controller pays {2}.
{2}{G}{ // }{4}{U}{U}
Spring // Mind
Sorcery // Instant
Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Aftermath (Cast this spell only from your graveyard. Then exile it.)
Draw two cards.
{1}
Stoneforge Masterwork
Artifact - Equipment
Equipped creature gets +1/+1 for each other creature you control that shares a creature type with it.
Equip {2}
{2}{U}
Supreme Will
Instant
Choose one --
• Counter target spell unless its controller pays {3}.
• Look at the top four cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.
--
Temple of Mystery
Land
Temple of Mystery enters the battlefield tapped.
When Temple of Mystery enters the battlefield, scry 1.
{T}: Add {G} or {U}.
--
Terramorphic Expanse
Land
{T}, Sacrifice Terramorphic Expanse: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{2}{U}{U}
Vizier of Many Faces
Creature - Shapeshifter Cleric
You may have Vizier of Many Faces enter the battlefield as a copy of any creature on the battlefield, except if Vizier of Many Faces was embalmed, the token has no mana cost, it's white, and it's a Zombie in addition to its other types.
Embalm {3}{U}{U}
0 /
0
{2}{U}
Watertrap Weaver
Creature - Merfolk Wizard
When Watertrap Weaver enters the battlefield, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.
2 /
2
{G/U}{G/U}{G/U}
Wistful Selkie
Creature - Merfolk Wizard
When Wistful Selkie enters the battlefield, draw a card.
2 /
2
{3}{U}
Wonder
Creature - Incarnation
Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.
2 /
2
{1}{G}
Woodland Changeling
Creature - Shapeshifter
Changeling (This card is every creature type.)
2 /
2
--
Yavimaya Coast
Land
{T}: Add {C}.
{T}: Add {G} or {U}. Yavimaya Coast deals 1 damage to you.