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.
{2}{U}
As Foretold
Enchantment
At the beginning of your upkeep, put a time counter on As Foretold.
Once each turn, you may pay {0} rather than pay the mana cost for a spell you cast with mana value X or less, where X is the number of time counters on As Foretold.
{2}{U}{U}
Bident of Thassa
Legendary Enchantment Artifact
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.
{X}{U}{U}{U}
Blue Sun's Zenith
Instant
Target player draws X cards. Shuffle Blue Sun's Zenith into its owner's library.
{U}
Brainstorm
Instant
Draw three cards, then put two cards from your hand on top of your library in any order.
--
Buried Ruin
Land
{T}: Add {C}.
{2}, {T}, Sacrifice Buried Ruin: Return target artifact card from your graveyard to your hand.
{3}{U}
Call to the Kindred
Enchantment - Aura
Enchant creature
At the beginning of your upkeep, you may look at the top five cards of your library. If you do, you may put a creature card that shares a creature type with enchanted creature from among them onto the battlefield, then you put the rest of those cards on the bottom of your library in any order.
{1}{U}{U}
Cancel
Instant
Counter target spell.
{1}{U}{U}
Capsize
Instant
Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Return target permanent to its owner's hand.
{5}{U}{U}
Colossal Whale
Creature - Whale
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever Colossal Whale attacks, you may exile target creature defending player controls until Colossal Whale leaves the battlefield. (That creature returns under its owner's control.)
5 /
5
{1}{U}
Convincing Mirage
Enchantment - Aura
Enchant land
As Convincing Mirage enters the battlefield, choose a basic land type.
Enchanted land is the chosen type.
--
Coral Atoll
Land
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}.
{1}{U}
Coral Fighters
Creature - Merfolk Soldier
Whenever Coral Fighters attacks and isn't blocked, look at the top card of defending player's library. You may put that card on the bottom of that player's library.
1 /
1
{U}{U}
Coralhelm Commander
Creature - Merfolk Soldier
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.
2 /
2
{U}{U}
Counterspell
Instant
Counter target spell.
{U}
Cursecatcher
Creature - Merfolk Wizard
Sacrifice Cursecatcher: Counter target instant or sorcery spell unless its controller pays {1}.
1 /
1
{1}{U}
Cyclonic Rift
Instant
Return target nonland permanent you don't control to its owner's hand.
Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")
{3}{U}{U}
Desertion
Instant
Counter target spell. If an artifact or creature spell is countered this way, put that card onto the battlefield under your control instead of into its owner's graveyard.
{2}{U}{U}
Dissipation Field
Enchantment
Whenever a permanent deals damage to you, return it to its owner's hand.
{3}{U}{U}
Empress Galina
Legendary Creature - Merfolk Noble
{U}{U}, {T}: Gain control of target legendary permanent. (This effect lasts indefinitely.)
1 /
3
{U}
Enclave Cryptologist
Creature - Merfolk Wizard
Level up {1}{U} ({1}{U}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 1-2
0/1
{T}: Draw a card, then discard a card.
LEVEL 3+
0/1
{T}: Draw a card.
0 /
1
{3}{U}
Engulf the Shore
Instant
Return to their owners' hands all creatures with toughness less than or equal to the number of Islands you control.
{1}{U}
Essence Scatter
Instant
Counter target creature spell.
{3}{U}{U}
Evacuation
Instant
Return all creatures to their owners' hands.
--
Evolving Wilds
Land
{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
--
Field of Ruin
Land
{T}: Add {C}.
{2}, {T}, Sacrifice Field of Ruin: Destroy target nonbasic land an opponent controls. Each player searches their library for a basic land card, puts it onto the battlefield, then shuffles.
{5}{U}{U}
Fleet Swallower
Creature - Fish
Whenever Fleet Swallower attacks, target player mills half their library, rounded up.
6 /
6
--
Halimar Depths
Land
Halimar Depths enters the battlefield tapped.
When Halimar Depths enters the battlefield, look at the top three cards of your library, then put them back in any order.
{T}: Add {U}.
--
Ice Floe
Land
You may choose not to untap Ice Floe during your untap step.
{T}: Tap target creature without flying that's attacking you. It doesn't untap during its controller's untap step for as long as Ice Floe remains tapped.
{7}{U}{U}
Inkwell Leviathan
Artifact Creature - Leviathan
Trample
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Shroud (This creature can't be the target of spells or abilities.)
7 /
11
--
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}.)
{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
{U}{U}
Lord of Atlantis
Creature - Merfolk
Other Merfolk get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)
2 /
2
{3}{U}
Master of Waves
Creature - Merfolk Wizard
Protection from red
Elemental creatures you control get +1/+1.
When Master of Waves enters the battlefield, create a number of 1/0 blue Elemental creature tokens equal to your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)
2 /
1
{U}{U}
Master of the Pearl Trident
Creature - Merfolk
Other Merfolk creatures you control get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)
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
{1}{U}
Merrow Commerce
Tribal Enchantment - Merfolk
At the beginning of your end step, untap all Merfolk you control.
{3}{U}
Merrow Harbinger
Creature - Merfolk Wizard
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.
2 /
3
{2}{U}
Merrow Reejerey
Creature - Merfolk Soldier
Other Merfolk creatures you control get +1/+1.
Whenever you cast a Merfolk spell, you may tap or untap target permanent.
2 /
2
{2}
Metallic Mimic
Artifact Creature - Shapeshifter
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.
2 /
1
--
Mirrorpool
Land
Mirrorpool enters the battlefield tapped.
{T}: Add {C}.
{2}{C}, {T}, Sacrifice Mirrorpool: Copy target instant or sorcery spell you control. You may choose new targets for the copy.
{4}{C}, {T}, Sacrifice Mirrorpool: Create a token that's a copy of target creature you control.
--
Myriad Landscape
Land
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.
--
Mystifying Maze
Land
{T}: Add {C}.
{4}, {T}: Exile target attacking creature an opponent controls. At the beginning of the next end step, return it to the battlefield tapped under its owner's control.
{1}{U}
Negate
Instant
Counter target noncreature spell.
--
Nykthos, Shrine to Nyx
Legendary Land
{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.)
{1}{U}
Phantasmal Image
Creature - Illusion
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."
0 /
0
{U}
Ponder
Sorcery
Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.
{2}{U}
Propaganda
Enchantment
Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.
{3}
Proteus Staff
Artifact
{2}{U}, {T}: Put target creature on the bottom of its owner's library. That creature's controller reveals cards from the top of their library until they reveal a creature card. The player puts that card onto the battlefield and the rest on the bottom of their library in any order. Activate only as a sorcery.
{X}{U}{U}
Pull from Tomorrow
Instant
Draw X cards, then discard a card.
{3}
Quicksilver Fountain
Artifact
At the beginning of each player's upkeep, that player puts a flood counter on target non-Island land they control of their choice. That land is an Island for as long as it has a flood counter on it.
At the beginning of each end step, if all lands on the battlefield are Islands, remove all flood counters from them.
{1}{U}
Reality Shift
Instant
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.)
--
Reliquary Tower
Land
You have no maximum hand size.
{T}: Add {C}.
{2}{U}{U}
Rite of Replication
Sorcery
Kicker {5} (You may pay an additional {5} as you cast this spell.)
Create a token that's a copy of target creature. If this spell was kicked, create five of those tokens instead.
{1}{U}
Rootwater Thief
Creature - Merfolk Rogue
{U}: Rootwater Thief gains flying until end of turn.
Whenever Rootwater Thief deals combat damage to a player, you may pay {2}. If you do, search that player's library for a card and exile it, then the player shuffles.
1 /
2
{2}{U}
Sage of Fables
Creature - Merfolk Wizard
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.
2 /
2
--
Sand Silos
Land
Sand Silos enters the battlefield tapped.
You may choose not to untap Sand Silos during your untap step.
At the beginning of your upkeep, if Sand Silos is tapped, put a storage counter on it.
{T}, Remove any number of storage counters from Sand Silos: Add {U} for each storage counter removed this way.
{1}{U}
Saprazzan Heir
Creature - Merfolk
Whenever Saprazzan Heir becomes blocked, you may draw three cards.
1 /
1
{1}{U}
Sea Scryer
Creature - Merfolk Wizard
{T}: Add {C}.
{1}, {T}: Add {U}.
1 /
1
{U}
Sea's Claim
Enchantment - Aura
Enchant land (Target a land as you cast this. This card enters the battlefield attached to that land.)
Enchanted land is an Island.
{2}{U}{U}
Seahunter
Creature - Human Mercenary
{3}, {T}: Search your library for a Merfolk permanent card, put it onto the battlefield, then shuffle.
2 /
2
{1}{U}{U}
Seasinger
Creature - Merfolk
When you control no Islands, sacrifice Seasinger.
You may choose not to untap Seasinger during your untap step.
{T}: Gain control of target creature whose controller controls an Island for as long as you control Seasinger and Seasinger remains tapped.
0 /
1
{1}{U}{U}
Sigil Tracer
Creature - Merfolk Wizard
{1}{U}, Tap two untapped Wizards you control: Copy target instant or sorcery spell. You may choose new targets for the copy.
2 /
2
{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
{1}{U}
Silvergill Douser
Creature - Merfolk Wizard
{T}: Target creature gets -X/-0 until end of turn, where X is the number of Merfolk and/or Faeries you control.
1 /
1
--
Skyline Cascade
Land
Skyline Cascade enters the battlefield tapped.
When Skyline Cascade enters the battlefield, target creature an opponent controls doesn't untap during its controller's next untap step.
{T}: Add {U}.
{1}
Sol Ring
Artifact
{T}: Add {C}{C}.
{1}{U}
Spreading Seas
Enchantment - Aura
Enchant land
When Spreading Seas enters the battlefield, draw a card.
Enchanted land is an Island.
{1}{U}
Stonybrook Angler
Creature - Merfolk Wizard
{1}{U}, {T}: You may tap or untap target creature.
1 /
2
{1}{U}
Stonybrook Banneret
Creature - Merfolk Wizard
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.
1 /
1
{5}{U}{U}{U}
Stormtide Leviathan
Creature - Leviathan
Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
All lands are Islands in addition to their other types.
Creatures without flying or islandwalk can't attack.
8 /
8
{1}{U}{U}
Streambed Aquitects
Creature - Merfolk Scout
{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.
2 /
3
--
Svyelunite Temple
Land
Svyelunite Temple enters the battlefield tapped.
{T}: Add {U}.
{T}, Sacrifice Svyelunite Temple: Add {U}{U}.
{X}{U}
Syncopate
Instant
Counter target spell unless its controller pays {X}. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.
--
Tectonic Edge
Land
{T}: Add {C}.
{1}, {T}, Sacrifice Tectonic Edge: Destroy target nonbasic land. Activate only if an opponent controls four or more lands.
--
Terramorphic Expanse
Land
{T}, Sacrifice Terramorphic Expanse: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{1}{U}{U}
Thada Adel, Acquisitor
Legendary Creature - Merfolk Rogue
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.
2 /
2
{2}{U}
Thassa, God of the Sea
Legendary Enchantment Creature - God
Indestructible
As long as your devotion to blue is less than five, Thassa isn't a creature. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)
At the beginning of your upkeep, scry 1.
{1}{U}: Target creature you control can't be blocked this turn.
5 /
5
{2}
Thaumatic Compass
Artifact
{3}, {T}: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
At the beginning of your end step, if you control seven or more lands, transform Thaumatic Compass.
--
Spires of Orazca
Land
(Transforms from Thaumatic Compass.)
{T}: Add {C}.
{T}: Untap target attacking creature an opponent controls and remove it from combat.
{2}
Thaumatic Compass
Artifact
{3}, {T}: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
At the beginning of your end step, if you control seven or more lands, transform Thaumatic Compass.
--
Spires of Orazca
Land
(Transforms from Thaumatic Compass.)
{T}: Add {C}.
{T}: Untap target attacking creature an opponent controls and remove it from combat.
{3}{U}
Tidal Courier
Creature - Merfolk
When Tidal Courier enters the battlefield, reveal the top four cards of your library. Put all Merfolk cards revealed this way into your hand and the rest on the bottom of your library in any order.
{3}{U}: Tidal Courier gains flying until end of turn.
1 /
2
{2}{U}
Trinket Mage
Creature - Human Wizard
When Trinket Mage enters the battlefield, you may search your library for an artifact card with mana value 1 or less, reveal that card, put it into your hand, then shuffle.
2 /
2
{U}
Triton Shorestalker
Creature - Merfolk Rogue
Triton Shorestalker can't be blocked.
1 /
1
{1}{U}{U}
True-Name Nemesis
Creature - Merfolk Rogue
As True-Name Nemesis enters the battlefield, choose a player.
True-Name Nemesis has protection from the chosen player.
3 /
1
{2}{U}
Vodalian Illusionist
Creature - Merfolk Wizard
{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.)
2 /
2
{2}{U}
Wake Thrasher
Creature - Merfolk Soldier
Whenever a permanent you control becomes untapped, Wake Thrasher gets +1/+1 until end of turn.
1 /
1
{4}{U}{U}
Wanderwine Prophets
Creature - Merfolk Wizard
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.
4 /
4
--
Warped Landscape
Land
{T}: Add {C}.
{2}, {T}, Sacrifice Warped Landscape: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
{3}{U}{U}
Waterspout Weavers
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 Waterspout Weavers, you may reveal it. If you do, each creature you control gains flying until end of turn.