Nemesis of Reason

Whenever this creature attacks, defending player mills ten cards.

Fraying Sanity

Enchant player
At the beginning of each end step, enchanted player mills X cards, where X is the number of cards put into their graveyard from anywhere this turn.

Maddening Cacophony

Kicker {3}{U}
Each opponent mills eight cards. If this spell was kicked, instead each opponent mills half their library, rounded up.

Glimpse the Unthinkable

Mind Funeral

Target opponent reveals cards from the top of their library until four land cards are revealed. That player puts all cards revealed this way into their graveyard.

Wight of Precinct Six

This creature gets +1/+1 for each creature card in your opponents' graveyards.

Death's Approach

Enchant creature
Enchanted creature gets -X/-X, where X is the number of creature cards in its controller's graveyard.

Watery Grave

({T}: Add {U} or {B}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Grisly Spectacle

Destroy target nonartifact creature. Its controller mills cards equal to that creature's power.

Swamp

Fractured Sanity

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

Jace's Phantasm

Flying
This creature gets +4/+4 as long as an opponent has ten or more cards in their graveyard.

Consuming Aberration

Consuming Aberration's power and toughness are each equal to the number of cards in your opponents' graveyards.
Whenever you cast a spell, each opponent reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

Phenax, God of Deception

Indestructible
As long as your devotion to blue and black is less than seven, Phenax isn't a creature.
Creatures you control have "{T}: Target player mills X cards, where X is this creature's toughness."

Island

Drowned Catacomb

This land enters tapped unless you control an Island or a Swamp.
{T}: Add {U} or {B}.

Mind Sculpt

Paranoid Delusions

Target player mills three cards.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Ashiok, Nightmare Muse

+1: Create a 2/3 blue and black Nightmare creature token with "Whenever this token attacks or blocks, each opponent exiles the top two cards of their library."
−3: Return target nonland permanent to its owner's hand, then that player exiles a card from their hand.
−7: You may cast up to three spells from among face-up cards your opponents own from exile without paying their mana costs.