Pilfered Plans

Target player mills two cards. Draw two cards.

Mirelurk Queen

Vigilance
When Mirelurk Queen enters, target player gets two rad counters.
Whenever one or more nonland cards are milled, draw a card, then put a +1/+1 counter on Mirelurk Queen. This ability triggers only once each turn.

Swamp

Thought Scour

Target player mills two cards.
Draw a card.

Drowned Secrets

Whenever you cast a blue spell, target player mills two cards.

Jace's Erasure

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

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.

Fleet Swallower

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

Realmbreaker, the Invasion Tree

{2}, {T}: Target opponent mills three cards. Put a land card from their graveyard onto the battlefield tapped under your control. It gains "If this land would leave the battlefield, exile it instead of putting it anywhere else."
{10}, {T}, Sacrifice Realmbreaker, the Invasion Tree: Search your library for any number of Praetor cards, put them onto the battlefield, then shuffle.

Syr Konrad, the Grim

Whenever another creature dies, or a creature card is put into a graveyard from anywhere other than the battlefield, or a creature card leaves your graveyard, Syr Konrad, the Grim deals 1 damage to each opponent.
{1}{B}: Each player mills a card. (They each put the top card of their library into their graveyard.)

Didn't Say Please

Counter target spell. Its controller mills three cards.

Psychic Strike

Counter target spell. Its controller mills two cards.

Thought Collapse

Nemesis of Reason

Whenever Nemesis of Reason attacks, defending player mills ten cards.

Keening Stone

{5}, {T}: Target player mills X cards, where X is the number of cards in that player's graveyard.