Waterveil Cavern

{T}: Add {C}.
{T}: Add {U} or {B}. Waterveil Cavern doesn't untap during your next untap step.

Tainted Isle

{T}: Add {C}.
{T}: Add {U} or {B}. Activate only if you control a Swamp.

Deprive

As an additional cost to cast this spell, return a land you control to its owner's hand.
Counter target spell.

Jace's Mindseeker

Flying
When Jace's Mindseeker enters, target opponent mills five cards. You may cast an instant or sorcery spell from among them without paying its mana cost.

Jinxed Ring

Whenever a nontoken permanent is put into your graveyard from the battlefield, Jinxed Ring deals 1 damage to you.
Sacrifice a creature: Target opponent gains control of Jinxed Ring. (This effect lasts indefinitely.)

Thieves' Guild Enforcer

Flash
Whenever Thieves' Guild Enforcer or another Rogue you control enters, each opponent mills two cards.
As long as an opponent has eight or more cards in their graveyard, Thieves' Guild Enforcer gets +2/+1 and has deathtouch.

Countermand

Counter target spell. Its controller mills four cards.

Mind Slash

{B}, Sacrifice a creature: Target opponent reveals their hand. You choose a card from it. That player discards that card. Activate only as a sorcery.

Long Goodbye

This spell can't be countered. (This includes by the ward ability.)
Destroy target creature or planeswalker with mana value 3 or less.

Witch's Oven

{T}, Sacrifice a creature: Create a Food token. If the sacrificed creature's toughness was 4 or greater, create two Food tokens instead. (They're artifacts with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")

Thopter Spy Network

At the beginning of your upkeep, if you control an artifact, create a 1/1 colorless Thopter artifact creature token with flying.
Whenever one or more artifact creatures you control deal combat damage to a player, draw a card.

Free the Fae

Mill four cards. Then put an instant, sorcery, or Faerie card from among the milled cards into your hand.

Picklock Prankster

Picklock Prankster // Free the Fae

Thought Collapse

Counter target spell. Its controller mills three cards.

Master of Etherium

Master of Etherium's power and toughness are each equal to the number of artifacts you control.
Other artifact creatures you control get +1/+1.

Deal Gone Bad

Target creature gets -3/-3 until end of turn. Target player mills three cards. (They put the top three cards of their library into their graveyard.)

Naiad of Hidden Coves

During turns other than yours, spells you cast cost {1} less to cast.

Foundry Inspector

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

Creeping Tar Pit

Creeping Tar Pit enters tapped.
{T}: Add {U} or {B}.
{1}{U}{B}: Creeping Tar Pit becomes a 3/2 blue and black Elemental creature until end of turn and can't be blocked this turn. It's still a land.

Stormscape Familiar

Flying
White spells and black spells you cast cost {1} less to cast.

Helm of Awakening

Chief Engineer

Artifact spells you cast have convoke. (Your creatures can help cast those spells. Each creature you tap while casting an artifact spell pays for {1} or one mana of that creature's color.)

Manic Scribe

When Manic Scribe enters, each opponent mills three cards.
Delirium — At the beginning of each opponent's upkeep, if there are four or more card types among cards in your graveyard, that player mills three cards.

Ambassador Laquatus

Arcane Signet

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

Glacial Grasp

Tap target creature. Its controller mills two cards. That creature doesn't untap during its controller's next untap step. (They put the top two cards of their library into their graveyard.)
Draw a card.

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.)

Sol Ring

Raul, Trouble Shooter

Once during each of your turns, you may cast a spell from among cards in your graveyard that were milled this turn.
{T}: Each player mills a card. (They each put the top card of their library into their graveyard.)

The Cyber-Controller

When The Cyber-Controller enters, each opponent mills X cards. Put all creature cards milled this way onto the battlefield face down under your control. They're 2/2 Cyberman artifact creatures.
Other artifact creatures you control get +1/+1.

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.)

Psychic Spiral

Shuffle all cards from your graveyard into your library. Target player mills that many cards.

Inspiring Statuary

Nonartifact spells you cast have improvise. (Your artifacts can help cast those spells. Each artifact you tap after you're done activating mana abilities pays for {1}.)

Dimir Charm

Choose one —
• Counter target sorcery spell.
• Destroy target creature with power 2 or less.
• Look at the top three cards of target player's library. Put one back and the rest into that player's graveyard.

Bad River

Bad River enters tapped.
{T}, Sacrifice Bad River: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

River of Tears

{T}: Add {U}. If you played a land this turn, add {B} instead.

Winds of Rebuke

Return target nonland permanent to its owner's hand. Each player mills two cards.

Nightscape Familiar

Blue spells and red spells you cast cost {1} less to cast.
{1}{B}: Regenerate Nightscape Familiar.

Geyser Drake

Flying
During turns other than yours, spells you cast cost {1} less to cast.

Deadly Tempest

Destroy all creatures. Each player loses life equal to the number of creatures they controlled that were destroyed this way.

Command Tower

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.

Fuel for the Cause

Counter target spell, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Ob Nixilis of the Black Oath

+2: Each opponent loses 1 life. You gain life equal to the life lost this way.
−2: Create a 5/5 black Demon creature token with flying. You lose 2 life.
−8: You get an emblem with "{1}{B}, Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power."
Ob Nixilis of the Black Oath can be your commander.

Jinxed Idol

At the beginning of your upkeep, Jinxed Idol deals 2 damage to you.
Sacrifice a creature: Target opponent gains control of Jinxed Idol.

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.)

Etrata, Deadly Fugitive

Deathtouch
Face-down creatures you control have "{2}{U}{B}: Turn this creature face up. If you can't, exile it, then you may cast the exiled card without paying its mana cost."
Whenever an Assassin you control deals combat damage to an opponent, cloak the top card of that player's library.

Ray of Erasure

Target player mills a card.
Draw a card at the beginning of the next turn's upkeep.

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.

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.

Contaminated Aquifer

({T}: Add {U} or {B}.)
Contaminated Aquifer enters tapped.

Didn't Say Please

Font of Magic

Instant and sorcery spells you cast cost {1} less to cast for each time you've cast a commander from the command zone this game.

Ghoulcaller's Bell

Magnetic Flux

Artifact creatures you control gain flying until end of turn.

Cathartic Adept

Swamp

Fallaji Archaeologist

When Fallaji Archaeologist enters, mill three cards. You may put a noncreature, nonland card from among the cards milled this way into your hand. If you don't, put a +1/+1 counter on Fallaji Archaeologist. (To mill a card, put the top card of your library into your graveyard.)

Soratami Mindsweeper

Flying
{2}, Return a land you control to its owner's hand: Target player mills two cards.

Kefnet's Monument

Blue creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, target creature an opponent controls doesn't untap during its controller's next untap step.

Blood on the Snow

Choose one —
• Destroy all creatures.
• Destroy all planeswalkers.
Then return a creature or planeswalker card with mana value X or less from your graveyard to the battlefield, where X is the amount of {S} spent to cast this spell. ({S} is mana from a snow source.)

Sprite Noble

Flying
Other creatures you control with flying get +0/+1.
{T}: Other creatures you control with flying get +1/+0 until end of turn.

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.)

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.)

Restless Reef

Restless Reef enters tapped.
{T}: Add {U} or {B}.
{2}{U}{B}: Until end of turn, Restless Reef becomes a 4/4 blue and black Shark creature with deathtouch. It's still a land.
Whenever Restless Reef attacks, target player mills four cards.

Jhoira's Familiar

Flying
Historic spells you cast cost {1} less to cast. (Artifacts, legendaries, and Sagas are historic.)

Etherium Sculptor

Archway of Innovation

Archway of Innovation enters tapped unless you control an Island.
{T}: Add {U}.
{U}, {T}: The next spell you cast this turn has improvise. (Your artifacts can help cast that spell. Each artifact you tap after you're done activating mana abilities pays for {1}.)

Star Whale

Flying, vigilance
Other creatures you control have ward {2}.
Suspend 6—{1}{U} (Rather than cast this card from your hand, you may pay {1}{U} and exile it with six time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Wonder

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

Thought Scour

Target player mills two cards.
Draw a card.

Devour in Shadow

Destroy target creature. It can't be regenerated. You lose life equal to that creature's toughness.

Chief of the Foundry

Other artifact creatures you control get +1/+1.

Shadow Kin

Flash
At the beginning of your upkeep, each player mills three cards. You may exile a creature card from among the cards milled this way. If you do, Shadow Kin becomes a copy of that card, except it has this ability.

Culling Dais

{T}, Sacrifice a creature: Put a charge counter on Culling Dais.
{1}, Sacrifice Culling Dais: Draw a card for each charge counter on Culling Dais.

Island

Vision Charm

Choose one —
• Target player mills four cards.
• Choose a land type and a basic land type. Each land of the first chosen type becomes the second chosen type until end of turn.
• Target artifact phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before its controller untaps during their next untap step.)