Disturbing Conversion

Flash
Enchant creature
When Disturbing Conversion enters, each player mills two cards.
Enchanted creature gets -X/-0, where X is the number of cards in its controller's graveyard.

Tome Scour

Towering-Wave Mystic

Whenever Towering-Wave Mystic deals damage, target player mills that many cards.

Ghoulcaller's Bell

Compelling Argument

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

Thassa's Devourer

Constellation — Whenever Thassa's Devourer or another enchantment you control enters, target player mills two cards.

Reef Pirates

Whenever Reef Pirates deals damage to an opponent, that player mills a card.

Halo-Charged Skaab

When Halo-Charged Skaab enters, each player mills two cards. Then you may put an instant, sorcery, or battle card from your graveyard on top of your library. (To mill two cards, a player puts the top two cards of their library into their graveyard.)

Vedalken Entrancer

Rotcrown Ghoul

When Rotcrown Ghoul dies, target player mills five cards.

Jace's Erasure

Whenever you draw a card, you may have target player mill a card.

Stream of Thought

Target player mills four cards. You shuffle up to four cards from your graveyard into your library.
Replicate {2}{U}{U} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)

Cathartic Adept

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

Ray of Erasure

Target player mills a card.
Draw a card at the beginning of the next turn's upkeep.

Didn't Say Please

Counter target spell. Its controller mills three cards.

Evanescent Intellect

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

Merfolk Mesmerist

Doorkeeper

Defender
{2}{U}, {T}: Target player mills X cards, where X is the number of creatures you control with defender.

Crosstown Courier

Whenever Crosstown Courier deals combat damage to a player, that player mills that many cards.

Dreadwaters

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

Thought Scour

Target player mills two cards.
Draw a card.

Homarid Explorer

When Homarid Explorer enters, target player mills four cards.

Ruin Crab

Landfall — Whenever a land you control enters, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

Selhoff Occultist

Whenever Selhoff Occultist or another creature dies, target player mills a card.

Shriekgeist

Flying
Whenever Shriekgeist deals combat damage to a player, that player mills two cards.

Thassa's Bounty

Draw three cards. Target player mills three cards.

Chronic Flooding

Enchant land
Whenever enchanted land becomes tapped, its controller mills three cards.

Shriekhorn

Shriekhorn enters with three charge counters on it.
{T}, Remove a charge counter from Shriekhorn: Target player mills two cards.

Thought Collapse

Drownyard Amalgam

When Drownyard Amalgam enters, target player mills three cards. (They put the top three cards of their library into their graveyard.)
{2}{U}: Drownyard Amalgam can't be blocked this turn.

Glacial Grasp

Tap target creature. Its controller mills two cards. That creature doesn't untap during its controller's next untap step. (They put the top two cards of their library into their graveyard.)
Draw a card.

Drowner Initiate

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

Vision Charm

Choose one —
• Target player mills four cards.
• Choose a land type and a basic land type. Each land of the first chosen type becomes the second chosen type until end of turn.
• Target artifact 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.)

Curse of the Bloody Tome

Enchant player
At the beginning of enchanted player's upkeep, that player mills two cards.

Winds of Rebuke

Return target nonland permanent to its owner's hand. Each player mills two cards.

Countermand

Counter target spell. Its controller mills four cards.

Dream Twist

Target player mills three cards.
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Screeching Silcaw

Flying
Metalcraft — Whenever Screeching Silcaw deals combat damage to a player, if you control three or more artifacts, that player mills four cards.