Muddle the Mixture

Counter target instant or sorcery spell.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Island

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice Mind Stone: Draw a card.

Dismal Backwater

Dismal Backwater enters tapped.
When Dismal Backwater enters, you gain 1 life.
{T}: Add {U} or {B}.

Duskmantle Guildmage

{1}{U}{B}: Whenever a card is put into an opponent's graveyard from anywhere this turn, that player loses 1 life.
{2}{U}{B}: Target player mills two cards.

Evil Twin

You may have Evil Twin enter as a copy of any creature on the battlefield, except it has "{U}{B}, {T}: Destroy target creature with the same name as this creature."

Charcoal Diamond

Charcoal Diamond enters tapped.
{T}: Add {B}.

Court of Cunning

When Court of Cunning enters, you become the monarch.
At the beginning of your upkeep, any number of target players each mill two cards. If you're the monarch, each of those players mills ten cards instead. (To mill a card, a player puts the top card of their library into their graveyard.)

Wight of Precinct Six

Wight of Precinct Six gets +1/+1 for each creature card in your opponents' graveyards.

Didn't Say Please

Counter target spell. Its controller mills three 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.

Balustrade Spy

Flying
When Balustrade Spy enters, target player reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

Mirko Vosk, Mind Drinker

Flying
Whenever Mirko Vosk, Mind Drinker deals combat damage to a player, that player reveals cards from the top of their library until they reveal four land cards, then puts those cards into their graveyard.

Psychic Drain

Target player mills X cards and you gain X life.

Avatar of Woe

If there are ten or more creature cards total in all graveyards, this spell costs {6} less to cast.
Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
{T}: Destroy target creature. It can't be regenerated.

Mind Grind

Each opponent reveals cards from the top of their library until they reveal X land cards, then puts all cards revealed this way into their graveyard. X can't be 0.

Merchant Scroll

Search your library for a blue instant card, reveal that card, put it into your hand, then shuffle.

Maddening Cacophony

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

Aqueous Form

Enchant creature
Enchanted creature can't be blocked.
Whenever enchanted creature attacks, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Sky Diamond

Clever Impersonator

You may have Clever Impersonator enter as a copy of any nonland permanent on the battlefield.

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.)

Mnemonic Betrayal

Exile all opponents' graveyards. You may cast spells from among those cards this turn, and mana of any type can be spent to cast them. At the beginning of the next end step, if any of those cards remain exiled, return them to their owners' graveyards.
Exile Mnemonic Betrayal.

Stunt Double

Flash
You may have Stunt Double enter as a copy of any creature on the battlefield.

Visions of Beyond

Draw a card. If a graveyard has twenty or more cards in it, draw three cards instead.

Spell Crumple

Counter target spell. If that spell is countered this way, put it on the bottom of its owner's library instead of into that player's graveyard. Put Spell Crumple on the bottom of its owner's library.

Dimir Aqueduct

Dimir Aqueduct enters tapped.
When Dimir Aqueduct enters, return a land you control to its owner's hand.
{T}: Add {U}{B}.

Geth, Lord of the Vault

Intimidate (This creature can't be blocked except by artifact creatures and/or creatures that share a color with it.)
{X}{B}: Put target artifact or creature card with mana value X from an opponent's graveyard onto the battlefield under your control tapped. Then that player mills X cards.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Swamp

Wall of Stolen Identity

You may have Wall of Stolen Identity enter as a copy of any creature on the battlefield, except it's a Wall in addition to its other types and has defender. When you do, tap the copied creature and it doesn't untap during its controller's untap step for as long as you control Wall of Stolen Identity.

Extract from Darkness

Each player mills two cards. Then you put a creature card from a graveyard onto the battlefield under your control.

Dimir Guildgate

Dimir Guildgate enters tapped.
{T}: Add {U} or {B}.

Riddlekeeper

Whenever a creature attacks you or a planeswalker you control, that creature's controller mills two cards.

Victimize

Choose two target creature cards in your graveyard. Sacrifice a creature. If you do, return the chosen cards to the battlefield tapped.

Mindcrank

Whenever an opponent loses life, that player mills that many cards. (Damage causes loss of life.)

Oona, Queen of the Fae

Flying
{X}{U/B}: Choose a color. Target opponent exiles the top X cards of their library. For each card of the chosen color exiled this way, create a 1/1 blue and black Faerie Rogue creature token with flying.

Diabolic Tutor

Search your library for a card, put that card into your hand, then shuffle.

Archaeomancer

When Archaeomancer enters, return target instant or sorcery card from your graveyard to your hand.

Body Double

You may have Body Double enter as a copy of any creature card in a graveyard.

Traumatize

Target player mills half their library, rounded down.

Submerged Boneyard

Submerged Boneyard enters tapped.
{T}: Add {U} or {B}.

Dimir Doppelganger

{1}{U}{B}: Exile target creature card from a graveyard. Dimir Doppelganger becomes a copy of that card, except it has this ability.

Tunnel Vision

Choose a card name. Target player reveals cards from the top of their library until a card with that name is revealed. If it is, that player puts the rest of the revealed cards into their graveyard and puts the card with the chosen name on top of their library. Otherwise, the player shuffles.

Counterspell

Temple of Deceit

Temple of Deceit enters tapped.
When Temple of Deceit enters, scry 1.
{T}: Add {U} or {B}.

Lazav, Dimir Mastermind

Hexproof
Whenever a creature card is put into an opponent's graveyard from anywhere, you may have Lazav, Dimir Mastermind become a copy of that card, except its name is Lazav, Dimir Mastermind, it's legendary in addition to its other types, and it has hexproof and this ability.

Bonehoard

Living weapon (When this Equipment enters, create a 0/0 black Phyrexian Germ creature token, then attach this to it.)
Equipped creature gets +X/+X, where X is the number of creature cards in all graveyards.
Equip {2}

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.

Thought Collapse

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.

Sol Ring

Command Tower

Glimpse the Unthinkable

Dredge the Mire

Each opponent chooses a creature card in their graveyard. Put those cards onto the battlefield under your control.

Pilfered Plans

Target player mills two cards. Draw two cards.

Hedron Crab

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

Patient Rebuilding

At the beginning of your upkeep, target opponent mills three cards, then you draw a card for each land card put into their graveyard this way.

Grisly Spectacle

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

Nighthowler

Bestow {2}{B}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Nighthowler and enchanted creature each get +X/+X, where X is the number of creature cards in all graveyards.

Drowned Secrets

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

Terramorphic Expanse

{T}, Sacrifice Terramorphic Expanse: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Memory Erosion

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

Sphinx's Tutelage

Whenever you draw a card, target opponent mills two cards. If two nonland cards that share a color were milled this way, repeat this process.
{5}{U}: Draw a card, then discard a card.

Persistent Nightmare

Skulk (This creature can't be blocked by creatures with greater power.)
When Persistent Nightmare deals combat damage to a player, return it to its owner's hand.

Startled Awake

Target opponent mills thirteen cards.
{3}{U}{U}: Put Startled Awake from your graveyard onto the battlefield transformed. Activate only as a sorcery.

Startled Awake // Persistent Nightmare

Jwar Isle Refuge

Jwar Isle Refuge enters tapped.
When Jwar Isle Refuge enters, you gain 1 life.
{T}: Add {U} or {B}.

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Hinder

Counter target spell. If that spell is countered this way, put that card on the top or bottom of its owner's library instead of into that player's graveyard.

Evolving Wilds

{T}, Sacrifice Evolving Wilds: Search your library for a basic land card, put it onto the battlefield tapped, then shuffle.

Nemesis of Reason

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

Induce Paranoia

Counter target spell. If {B} was spent to cast this spell, that spell's controller mills X cards, where X is the spell's mana value.

Psychic Corrosion

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

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.)

Fleet Swallower

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