Drowner Initiate

Whenever a player casts a blue spell, you may pay {1}. If you do, target player mills two cards.

Merfolk Falconer

Flying
Whenever you cast a kicked spell, scry 2.

Zagoth Crystal

{T}: Add {B}, {G}, or {U}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Mystic Sanctuary

({T}: Add {U}.)
Mystic Sanctuary enters tapped unless you control three or more other Islands.
When Mystic Sanctuary enters untapped, you may put target instant or sorcery card from your graveyard on top of your library.

Dreadwaters

Target player mills X cards, where X is the number of lands you control.

Sure-Footed Infiltrator

Tap another untapped Rogue you control: Sure-Footed Infiltrator can't be blocked this turn.
Whenever Sure-Footed Infiltrator deals combat damage to a player, draw a card.

Cascade Seer

When Cascade Seer enters, scry X, where X is the number of creatures in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Stonybrook Angler

{1}{U}, {T}: You may tap or untap target creature.

Wishful Merfolk

Defender
{1}{U}: Wishful Merfolk loses defender and becomes a Human until end of turn.

Tazeem Roilmage

Kicker {4} (You may pay an additional {4} as you cast this spell.)
When Tazeem Roilmage enters, if it was kicked, return target instant or sorcery card from your graveyard to your hand.

Venture Deeper

Target player mills four cards. (Then exile this card. You may cast the creature later from exile.)

Merfolk Secretkeeper

Merfolk Secretkeeper // Venture Deeper

Rune Snag

Counter target spell unless its controller pays {2} plus an additional {2} for each card named Rune Snag in each graveyard.

Merrow Witsniper

When Merrow Witsniper enters, target player mills a card.

Fact or Fiction

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Expedition Diviner

Flying
As long as you control another Wizard, Expedition Diviner has "When this creature dies, draw a card."

Ertai's Scorn

This spell costs {U} less to cast if an opponent cast two or more spells this turn.
Counter target spell.

Wash Away

Cleave {1}{U}{U} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Counter target spell [that wasn't cast from its owner's hand].

Negate

Essence Scatter

Streambed Aquitects

{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.

Honored Heirloom

{T}: Add one mana of any color.
{2}, {T}: Exile target card from a graveyard.

Shaper Apprentice

Shaper Apprentice has flying as long as you control another Merfolk.

Merfolk Windrobber

Flying
Whenever Merfolk Windrobber deals combat damage to a player, that player mills a card. (They put the top card of their library into their graveyard.)
Sacrifice Merfolk Windrobber: Draw a card. Activate only if an opponent has eight or more cards in their graveyard.

Shipwreck Dowser

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
When this creature enters, return target instant or sorcery card from your graveyard to your hand.

Read the Tides

Choose one —
• Draw three cards.
• Return up to two target creatures to their owners' hands.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Into the Void

Return up to two target creatures to their owners' hands.

Ink Dissolver

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.

Cancel

Teferi's Wavecaster

Flash
When Teferi's Wavecaster enters, you may search your library and/or graveyard for a card named Teferi, Timeless Voyager, reveal it, and put it into your hand. If you search your library this way, shuffle.

Nyxborn Seaguard

Library Larcenist

Whenever Library Larcenist attacks, draw a card.

Skyclave Plunder

Look at the top X cards of your library, where X is three plus the number of creatures in your party. Put three of those cards into your hand and the rest on the bottom of your library in a random order. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

Dimir Locket

{T}: Add {U} or {B}.
{U/B}{U/B}{U/B}{U/B}, {T}, Sacrifice Dimir Locket: Draw two cards.

Silent Dart

{4}, {T}, Sacrifice Silent Dart: It deals 3 damage to target creature.

Wilderness Hypnotist

{T}: Target red or green creature gets -2/-0 until end of turn.

Thirst for Discovery

Draw three cards. Then discard two cards unless you discard a basic land card.

Moonlit Scavengers

When Moonlit Scavengers enters, if you control an artifact or enchantment, return target creature an opponent controls to its owner's hand.

Sage of the Falls

Whenever Sage of the Falls or another non-Human creature you control enters, you may draw a card. If you do, discard a card.

Shore Keeper

{7}{U}, {T}, Sacrifice Shore Keeper: Draw three cards.

Glimmer of Genius

Scry 2, then draw two cards. You get {E}{E} (two energy counters).

Mantle of Tides

Equipped creature gets +1/+2.
Whenever you draw your second card each turn, attach Mantle of Tides to target creature you control.
Equip {3} ({3}: Attach to target creature you control. Equip only as a sorcery.)

Brineborn Cutthroat

Flash (You may cast this spell any time you could cast an instant.)
Whenever you cast a spell during an opponent's turn, put a +1/+1 counter on this creature.