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.)

Merrow Witsniper

When Merrow Witsniper enters, target player mills a card.

Drowner Initiate

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

Mind Sculpt

Drowner of Secrets

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

Island

Mystic Redaction

At the beginning of your upkeep, scry 1.
Whenever you discard a card, each opponent mills two cards. (They put the top two cards of their library into their graveyard.)

Merfolk Looter

Psychic Corrosion

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

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

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.

Coerced Confession

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

Didn't Say Please

Counter target spell. Its controller mills three cards.

Run Away Together

Choose two target creatures controlled by different players. Return those creatures to their owners' hands.