Island

Reckless Scholar

{T}: Target player draws a card, then discards a card.

Lawless Broker

When Lawless Broker dies, put a +1/+1 counter on target creature you control.

Dreadwaters

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

Child of Night

Harsh Scrutiny

Target opponent reveals their hand. You choose a creature card from it. That player discards that card. Scry 1.

Tome Scour

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

Fleet Swallower

Whenever Fleet Swallower attacks, target player mills half their library, rounded up.

Wight of Precinct Six

Wight of Precinct Six gets +1/+1 for each creature card in your opponents' graveyards.

Mind Sculpt

Thought Scour

Target player mills two cards.
Draw a card.

Mortivore

Mortivore's power and toughness are each equal to the number of creature cards in all graveyards.
{B}: Regenerate Mortivore. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Siren of the Silent Song

Flying
Inspired — Whenever Siren of the Silent Song becomes untapped, each opponent discards a card, then each opponent mills a card.

Swamp

Shoreline Salvager

Whenever Shoreline Salvager deals combat damage to a player, if you control an Island, you may draw a card.

Compelling Argument

Target player mills five cards.
Cycling {U} ({U}, Discard this card: Draw a card.)

Coerced Confession

Target player mills four cards. You draw a card for each creature card put into their graveyard this way.

Submerged Boneyard

Submerged Boneyard enters tapped.
{T}: Add {U} or {B}.

Psychic Corrosion

Whenever you draw a card, each opponent mills two cards.

Trepanation Blade

Whenever equipped creature attacks, defending player reveals cards from the top of their library until they reveal a land card. The creature gets +1/+0 until end of turn for each card revealed this way. That player puts the revealed cards into their graveyard.
Equip {2}

Dismal Backwater

Dismal Backwater enters tapped.
When Dismal Backwater enters, you gain 1 life.
{T}: Add {U} or {B}.

Maritime Guard

Divest

Target player reveals their hand. You choose an artifact or creature card from it. That player discards that card.

Codex Shredder

{T}: Target player mills a card. (They put the top card of their library into their graveyard.)
{5}, {T}, Sacrifice Codex Shredder: Return target card from your graveyard to your hand.

Returned Centaur

When Returned Centaur enters, target player mills four cards.

Stormscape Familiar

Flying
White spells and black spells you cast cost {1} less to cast.

Evanescent Intellect

Enchant creature
Enchanted creature has "{1}{U}, {T}: Target player mills three cards."