Cathartic Adept

Demogorgon's Clutches

Target opponent discards two cards, mills two cards, and loses 2 life. (To mill a card, a player puts the top card of their library into their graveyard.)

Countermand

Counter target spell. Its controller mills four cards.

Hedron Crab

Landfall — Whenever a land you control enters, target player mills three cards.

Island

Chronic Flooding

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

Dimir Signet

Fractured Sanity

Each opponent mills fourteen cards.
Cycling {1}{U} ({1}{U}, Discard this card: Draw a card.)
When you cycle Fractured Sanity, each opponent mills four cards.

Ashiok, Dream Render

Spells and abilities your opponents control can't cause their controller to search their library.
−1: Target player mills four cards. Then exile each opponent's graveyard.

Polluted Delta

{T}, Pay 1 life, Sacrifice Polluted Delta: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

Didn't Say Please

Counter target spell. Its controller mills three cards.

Altar of the Brood

Whenever another permanent you control enters, each opponent mills a card.

Drowner Initiate

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

Swamp

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.)

Infernal Grasp

Destroy target creature. You lose 2 life.

Archive Trap

If an opponent searched their library this turn, you may pay {0} rather than pay this spell's mana cost.
Target opponent mills thirteen 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.)