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.

Zellix, Sanity Flayer

Hive Mind — Whenever a player mills one or more creature cards, you create a 1/1 black Horror creature token.
{1}, {T}: Target player mills three cards.
Choose a Background (You can have a Background as a second commander.)

Dreadwaters

Target player mills X cards, where X is the number of lands you control.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Archive Trap

If an opponent searched their library this turn, you may pay {0} rather than pay this spell's mana cost.
Target opponent mills thirteen cards.

Memory Erosion

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

Fleet Swallower

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

Traumatize

Target player mills half their library, rounded down.

Counterspell

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.)

Founding the Third Path

Read ahead (Choose a chapter and start with that many lore counters. Add one after your draw step. Skipped chapters don't trigger. Sacrifice after III.)
I — You may cast an instant or sorcery spell with mana value 1 or 2 from your hand without paying its mana cost.
II — Target player mills four cards.
III — Exile target instant or sorcery card from your graveyard. Copy it. You may cast the copy.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Chill of Foreboding

Each player mills five cards.
Flashback {7}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Jace, Memory Adept

+1: Draw a card. Target player mills a card.
0: Target player mills ten cards.
−7: Any number of target players each draw twenty cards.

Wall of Lost Thoughts

Defender (This creature can't attack.)
When Wall of Lost Thoughts enters, target player mills four cards. (They put the top four cards of their library into their graveyard.)

Fog Bank

Defender (This creature can't attack.)
Flying
Prevent all combat damage that would be dealt to and dealt by this creature.

Censor

Counter target spell unless its controller pays {1}.
Cycling {U} ({U}, Discard this card: Draw a card.)

Command Tower

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

Thought Scour

Target player mills two cards.
Draw a card.

Cathartic Adept

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.)

Coral Colony

Defender
{1}{U}, {T}: Target player mills X cards, where X is the number of creatures you control with defender. (To mill a card, a player puts the top card of their library into their graveyard.)

Arcane Signet

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.

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.

Jace, the Perfected Mind

Compleated ({U/P} can be paid with {U} or 2 life. If life was paid, this planeswalker enters with two fewer loyalty counters.)
+1: Until your next turn, up to one target creature gets -3/-0.
−2: Target player mills three cards. Then if a graveyard has twenty or more cards in it, you draw three cards. Otherwise, you draw a card.
−X: Target player mills three times X cards.

Sol Ring

Weathered Sentinels

Defender, vigilance, reach, trample
Weathered Sentinels can attack players who attacked you during their last turn as though it didn't have defender.
Whenever Weathered Sentinels attacks, it gets +3/+3 and gains indestructible until end of turn.

Dampen Thought

Target player mills four cards.
Splice onto Arcane {1}{U} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Vessel of Paramnesia

{U}, Sacrifice Vessel of Paramnesia: Target player mills three cards. Draw a card.

Codex Shredder

{T}: Target player mills a card. (They put the top card of their library into their graveyard.)
{5}, {T}, Sacrifice Codex Shredder: Return target card from your graveyard to your hand.

Tasha's Hideous Laughter

Each opponent exiles cards from the top of their library until that player has exiled cards with total mana value 20 or more.

Chronic Flooding

Enchant land
Whenever enchanted land becomes tapped, its controller mills three cards.

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.)

Command Beacon

{T}: Add {C}.
{T}, Sacrifice Command Beacon: Put your commander into your hand from the command zone.

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.)

Maddening Cacophony

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

Island

Drowner Initiate

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

Drowned Secrets

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

Cut Your Losses

Casualty 2 (As you cast this spell, you may sacrifice a creature with power 2 or greater. When you do, copy this spell and you may choose a new target for the copy.)
Target player mills half their library, rounded down.

Baral, Chief of Compliance

Instant and sorcery spells you cast cost {1} less to cast.
Whenever a spell or ability you control counters a spell, you may draw a card. If you do, discard a card.

Doorkeeper

Defender
{2}{U}, {T}: Target player mills X cards, where X is the number of creatures you control with defender.

Compelling Argument

Target player mills five cards.
Cycling {U} ({U}, Discard this card: Draw a card.)

Curse of the Bloody Tome

Enchant player
At the beginning of enchanted player's upkeep, that player mills two cards.

Jace's Phantasm

Flying
Jace's Phantasm gets +4/+4 as long as an opponent has ten or more cards in their graveyard.

Drown in Dreams

Choose one. If you control a commander as you cast this spell, you may choose both instead.
• Target player draws X cards.
• Target player mills twice X cards.

Silent Arbiter

No more than one creature can attack each combat.
No more than one creature can block each combat.

Countermand

Counter target spell. Its controller mills four cards.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Propaganda

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Fading Hope

Return target creature to its owner's hand. If its mana value was 3 or less, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Psychic Corrosion

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

Harbinger of the Seas

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

Hedron Crab

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

Frantic Inventory

Draw a card, then draw cards equal to the number of cards named Frantic Inventory in your graveyard.

Fleeting Memories

When Fleeting Memories enters, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")
Whenever you sacrifice a Clue, target player mills three cards.

Didn't Say Please

Counter target spell. Its controller mills three cards.

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.

Chancellor of the Spires

You may reveal this card from your opening hand. If you do, at the beginning of the first upkeep, each opponent mills seven cards.
Flying
When Chancellor of the Spires enters, you may cast target instant or sorcery card from an opponent's graveyard without paying its mana cost.

Terisian Mindbreaker

Whenever Terisian Mindbreaker attacks, defending player mills half their library, rounded up.
Unearth {1}{U}{U}{U} ({1}{U}{U}{U}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Glaring Spotlight

Creatures your opponents control with hexproof can be the targets of spells and abilities you control as though they didn't have hexproof.
{3}, Sacrifice Glaring Spotlight: Creatures you control gain hexproof until end of turn and can't be blocked this turn.