You may play an additional land on each of your turns.
Landfall -- Whenever a land enters the battlefield under your control, you may draw a card.
5 /
5
{2}
Arcane Signet
Artifact
{T}: Add one mana of any color in your commander's color identity.
--
Barkchannel Pathway
Land
{T}: Add {G}.
--
Tidechannel Pathway
Land
{T}: Add {U}.
{2}{G}
Beast Within
Instant
Destroy target permanent. Its controller creates a 3/3 green Beast creature token.
--
Botanical Sanctum
Land
Botanical Sanctum enters the battlefield tapped unless you control two or fewer other lands.
{T}: Add {G} or {U}.
{2}{G}
Branching Evolution
Enchantment
If one or more +1/+1 counters would be put on a creature you control, twice that many +1/+1 counters are put on that creature instead.
--
Breeding Pool
Land - Forest Island
({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.
{5}
Coat of Arms
Artifact
Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)
{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.
{U}
Cosi's Trickster
Creature - Merfolk Wizard
Whenever an opponent shuffles their library, you may put a +1/+1 counter on Cosi's Trickster.
1 /
1
{U}{U}
Counterspell
Instant
Counter target spell.
{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.
{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.")
{1}{G}
Deeproot Elite
Creature - Merfolk Warrior
Whenever another Merfolk enters the battlefield under your control, put a +1/+1 counter on target Merfolk you control.
1 /
1
{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.)
{1}{U}{U}
Disallow
Instant
Counter target spell, activated ability, or triggered ability. (Mana abilities can't be targeted.)
{4}
Door of Destinies
Artifact
As Door of Destinies enters the battlefield, choose a creature type.
Whenever you cast a spell of the chosen type, put a charge counter on Door of Destinies.
Creatures you control of the chosen type get +1/+1 for each charge counter on Door of Destinies.
{1}{U}
Dramatic Reversal
Instant
Untap all nonland permanents you control.
{3}{U}{U}
Empress Galina
Legendary Creature - Merfolk Noble
{U}{U}, {T}: Gain control of target legendary permanent. (This effect lasts indefinitely.)
1 /
3
--
Fabled Passage
Land
{T}, Sacrifice Fabled Passage: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Then if you control four or more lands, untap that land.
{1}{G}
Farseek
Sorcery
Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.
{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}.)
--
Ghost Quarter
Land
{T}: Add {C}.
{T}, Sacrifice Ghost Quarter: Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.
{3}{G}
Guardian Project
Enchantment
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.
{1}{G}{U}
Hadana's Climb
Legendary Enchantment
At the beginning of combat on your turn, put a +1/+1 counter on target creature you control. Then if that creature has three or more +1/+1 counters on it, transform Hadana's Climb.
--
Winged Temple of Orazca
Legendary Land
(Transforms from Hadana's Climb.)
{T}: Add one mana of any color.
{1}{G}{U}, {T}: Target creature you control gains flying and gets +X/+X until end of turn, where X is its power.
{3}{U}
Herald of Secret Streams
Creature - Merfolk Warrior
Creatures you control with +1/+1 counters on them can't be blocked.
2 /
3
{3}
Herald's Horn
Artifact
As Herald's Horn enters the battlefield, choose a creature type.
Creature spells you cast of the chosen type cost {1} less to cast.
At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.
{1}{G}
Heroic Intervention
Instant
Permanents you control gain hexproof and indestructible until end of turn.
--
Hinterland Harbor
Land
Hinterland Harbor enters the battlefield tapped unless you control a Forest or an Island.
{T}: Add {G} or {U}.
{2}{G}
Inspiring Call
Instant
Draw a card for each creature you control with a +1/+1 counter on it. Those creatures gain indestructible until end of turn. (Damage and effects that say "destroy" don't destroy them.)
--
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}
Isochron Scepter
Artifact
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.
{1}{G}{G}
Jadelight Ranger
Creature - Merfolk Scout Ranger
When Jadelight Ranger enters the battlefield, it explores, then it explores again. (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. Then repeat this process.)
2 /
1
--
Karn's Bastion
Land
{T}: Add {C}.
{4}, {T}: Proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
{3}{U}{U}
Kindred Discovery
Enchantment
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.
{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.
{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
{2}{U}{U}
Leyline of Anticipation
Enchantment
If Leyline of Anticipation is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.
{2}
Lightning Greaves
Artifact - Equipment
Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}
{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
{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
--
Lumbering Falls
Land
Lumbering Falls enters the battlefield tapped.
{T}: Add {G} or {U}.
{2}{G}{U}: Lumbering Falls becomes a 3/3 green and blue Elemental creature with hexproof until end of turn. It's still a land.
{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}{G}
Merfolk Branchwalker
Creature - Merfolk Scout
When Merfolk Branchwalker 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.)
2 /
1
{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}
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
--
Misty Rainforest
Land
{T}, Pay 1 life, Sacrifice Misty Rainforest: Search your library for a Forest or Island card, put it onto the battlefield, then shuffle.
{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
--
Mutavault
Land
{T}: Add {C}.
{1}: Mutavault becomes a 2/2 creature with all creature types until end of turn. It's still a land.
{U}
Mystical Tutor
Instant
Search your library for an instant or sorcery card, reveal it, then shuffle and put that card on top.
--
Polluted Delta
Land
{T}, Pay 1 life, Sacrifice Polluted Delta: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.
{U}
Pongify
Instant
Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.
{U}
Rapid Hybridization
Instant
Destroy target creature. It can't be regenerated. That creature's controller creates a 3/3 green Frog Lizard creature token.
--
Rejuvenating Springs
Land
Rejuvenating Springs enters the battlefield tapped unless you have two or more opponents.
{T}: Add {G} or {U}.
--
Reliquary Tower
Land
You have no maximum hand size.
{T}: Add {C}.
--
Scalding Tarn
Land
{T}, Pay 1 life, Sacrifice Scalding Tarn: Search your library for an Island or Mountain card, put it onto the battlefield, then shuffle.
--
Scavenger Grounds
Land - Desert
{T}: Add {C}.
{2}, {T}, Sacrifice a Desert: Exile all graveyards.
{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
{3}{G}{G}
Seedborn Muse
Creature - Spirit
Untap all permanents you control during each other player's untap step.
2 /
4
{G}{U}
Simic Ascendancy
Enchantment
{1}{G}{U}: Put a +1/+1 counter on target creature you control.
Whenever one or more +1/+1 counters are put on a creature you control, put that many growth counters on Simic Ascendancy.
At the beginning of your upkeep, if Simic Ascendancy has twenty or more growth counters on it, you win the game.
{6}{U}{U}
Slinn Voda, the Rising Deep
Legendary Creature - Leviathan
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.
8 /
8
{1}
Sol Ring
Artifact
{T}: Add {C}{C}.
{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
{1}{U}{U}
Svyelun of Sea and Sky
Legendary Creature - Merfolk God
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}.)
3 /
4
{U}
Swan Song
Instant
Counter target enchantment, instant, or sorcery spell. Its controller creates a 2/2 blue Bird creature token with flying.
{2}
Swiftfoot Boots
Artifact - Equipment
Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}
{3}{G}{U}
Tatyova, Benthic Druid
Legendary Creature - Merfolk Druid
Landfall -- Whenever a land enters the battlefield under your control, you gain 1 life and draw a card.
3 /
3
--
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}.
{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
{3}{U}{U}
Time Warp
Sorcery
Target player takes an extra turn after this one.
{5}{G}{U}
Tishana, Voice of Thunder
Legendary Creature - Merfolk Shaman
Tishana, Voice of Thunder's power and toughness are each equal to the number of cards in your hand.
You have no maximum hand size.
When Tishana enters the battlefield, draw a card for each creature you control.
* /
*
{2}{G}{G}
Triumph of the Hordes
Sorcery
Until end of turn, creatures you control get +1/+1 and gain trample and infect. (Creatures with infect deal damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{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
--
Unclaimed Territory
Land
As Unclaimed Territory 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.
{5}
Vanquisher's Banner
Artifact
As Vanquisher's Banner enters the battlefield, choose a creature type.
Creatures you control of the chosen type get +1/+1.
Whenever you cast a creature spell of the chosen type, draw a card.
--
Verdant Catacombs
Land
{T}, Pay 1 life, Sacrifice Verdant Catacombs: Search your library for a Swamp or Forest card, put it onto the battlefield, then shuffle.
{G}{U}{U}
Voidslime
Instant
Counter target spell, activated ability, or triggered ability. (Mana abilities can't be targeted.)
{1}{G}{U}
Vorel of the Hull Clade
Legendary Creature - Human Merfolk
{G}{U}, {T}: Double the number of each kind of counter on target artifact, creature, or land.
1 /
4
--
Windswept Heath
Land
{T}, Pay 1 life, Sacrifice Windswept Heath: Search your library for a Forest or Plains card, put it onto the battlefield, then shuffle.
--
Wooded Foothills
Land
{T}, Pay 1 life, Sacrifice Wooded Foothills: Search your library for a Mountain or Forest card, put it onto the battlefield, then shuffle.