Thought Collapse

Counter target spell. Its controller mills three cards.

Towering-Wave Mystic

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

Island

Bruvac the Grandiloquent

If an opponent would mill one or more cards, they mill twice that many cards instead. (To mill a card, a player puts the top card of their library into their graveyard.)

Thriving Isle

Thriving Isle enters tapped. As it enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Memory Erosion

Whenever an opponent casts a spell, that player mills two cards.

Vedalken Entrancer

Thought Scour

Target player mills two cards.
Draw a card.

Selhoff Occultist

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

Capture Sphere

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature
When Capture Sphere enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step.

Wall of Lost Thoughts

Defender
When Wall of Lost Thoughts enters, target player mills four cards.

Reckless Scholar

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

Teferi's Tutelage

When Teferi's Tutelage enters, draw a card, then discard a card.
Whenever you draw a card, target opponent mills two cards. (They put the top two cards of their library into their graveyard.)

Belltower Sphinx

Flying
Whenever a source deals damage to Belltower Sphinx, that source's controller mills that many cards.