At the beginning of each end step, if an opponent lost 3 or more life this turn, you may draw a card. (Damage causes loss of life.)

Exile target permanent with mana value 4 or greater.

Destroy target creature, enchantment, or planeswalker. Its controller creates two Map tokens. (They're artifacts with "{1}, {T}, Sacrifice this artifact: Target creature you control explores. Activate only as a sorcery.")

Destroy target nonartifact creature.

{W}, {T}: Harpoon Sniper deals X damage to target attacking or blocking creature, where X is the number of Merfolk you control.

Return all nonblue creatures to their owners' hands.

Choose one — • Return target multicolored permanent card with mana value 3 or less from your graveyard to the battlefield tapped. • Counter target instant or sorcery spell. • Destroy target creature or planeswalker with mana value 3 or less.

Choose three. You may choose the same mode more than once. • Until end of turn, target creature loses all abilities and has base power and toughness 1/1. • Target creature connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on that creature.) • Target player returns a creature card from their graveyard to their hand.

Exile target artifact or enchantment. If you cast this spell during your main phase, you may exile up to one other target artifact or enchantment.

Return all nonland permanents target player controls to their owner's hand.

{T}, Exile cards from your graveyard equal to the number of opponents you have: Target creature card in your graveyard gains encore until end of turn. The encore cost is equal to its mana cost. (Exile the creature card and pay its mana cost: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Blue creatures you control can't be blocked.

Tap an untapped Merfolk you control: Target player mills a card.

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.

{U}{U}, {T}: Gain control of target legendary permanent. (This effect lasts indefinitely.)

Whenever Grimoire Thief becomes tapped, exile the top three cards of target opponent's library face down. You may look at cards exiled with Grimoire Thief. {U}, Sacrifice Grimoire Thief: Turn all cards exiled with Grimoire Thief face up. Counter all spells with those names.

Inkfathom Infiltrator can't block and can't be blocked.

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.) {2}{U}{B}: Each unblocked creature has base power and toughness 4/1 until end of turn.

Whenever a Merfolk you control becomes tapped, you may gain 1 life.

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.

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.)

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.)

Other Merfolk creatures you control get +1/+1. {T}: Target Merfolk creature can't be blocked this turn.

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.

Other Merfolk creatures you control get +1/+1. Whenever you cast a Merfolk spell, you may tap or untap target permanent.

{T}: Target land becomes the basic land type of your choice until end of turn.

{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.

{3}, {T}: Search your library for a Merfolk permanent card, put it onto the battlefield, then shuffle.

{1}{U}, Tap two untapped Wizards you control: Copy target instant or sorcery spell. You may choose new targets for the copy.

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.

Whenever Stonybrook Schoolmaster becomes tapped, you may create a 1/1 blue Merfolk Wizard creature token.

Create two 1/1 blue Merfolk Wizard creature tokens. Tap four untapped Merfolk you control: Return Summon the School from your graveyard to your hand.

Whenever Surgespanner becomes tapped, you may pay {1}{U}. If you do, return target permanent to its owner's hand.

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.

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.

{T}: Target land becomes the basic land type of your choice until end of turn. Activate only during your turn.

Whenever you draw a card, put a +1/+1 counter on each other Merfolk and/or Knight you control.

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.

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.

Return all creature and planeswalker cards with mana value X or less from your graveyard to the battlefield. Exile Ascend from Avernus.

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.

Choose a creature type. Draw a card for each permanent you control of that type.

Whenever Fallowsage becomes tapped, you may draw a card.

Commander creatures you own have "Whenever you cast a spell that shares a creature type with this creature, draw a card. This ability triggers only once each turn."

Whenever equipped creature deals combat damage to a player, you draw that many cards. Equip {4} Equip Shaman, Warlock, or Wizard {1}

Whenever one or more nontoken Merfolk you control become tapped, create a 1/1 blue Merfolk creature token with hexproof.

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.)

Creatures don't untap during their controllers' untap steps. Whenever a creature enters the battlefield, untap all creatures.

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

Commander creatures you own have "When this creature enters the battlefield and at the beginning of your upkeep, each player may put two +1/+1 counters on a creature they control. For each opponent who does, you gain protection from that player until your next turn." (You can't be targeted, dealt damage, or enchanted by anything controlled by that player.)

Arcane Sanctum enters the battlefield tapped. {T}: Add {W}, {U}, or {B}.

As Choked Estuary enters the battlefield, you may reveal an Island or Swamp card from your hand. If you don't, Choked Estuary enters the battlefield tapped. {T}: Add {U} or {B}.

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

{1}, {T}: Add {U}{B}.

{T}: Add one mana of any color that a land an opponent controls could produce.

({T}: Add {U}.)

Path of Ancestry enters the battlefield tapped. {T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

({T}: Add {W}.)

As Port Town enters the battlefield, you may reveal a Plains or Island card from your hand. If you don't, Port Town enters the battlefield tapped. {T}: Add {W} or {U}.

({T}: Add {W} or {U}.) Prairie Stream enters the battlefield tapped unless you control two or more basic lands.

{1}, {T}: Add {W}{U}.

({T}: Add {U} or {B}.) Sunken Hollow enters the battlefield tapped unless you control two or more basic lands.

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

{1}, {T}: Add {W}{U}.

{1}, {T}: Add {U}{B}.

As Heraldic Banner enters the battlefield, choose a color. Creatures you control of the chosen color get +1/+0. {T}: Add one mana of the chosen color.

{1}, {T}: Add {W}{B}.

{T}: Add {C}. {1}, {T}: Add {U}.

Sky Diamond enters the battlefield tapped. {T}: Add {U}.

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

Equipped creature gets +1/+1. Whenever equipped creature attacks, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle. Equip {2}

You may cast target instant or sorcery card from an opponent's graveyard without paying its mana cost.