Brainstorm

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

Spectator Seating

Spectator Seating enters tapped unless you have two or more opponents.
{T}: Add {R} or {W}.

Spire Garden

Spire Garden enters tapped unless you have two or more opponents.
{T}: Add {R} or {G}.

Warp World

Each player shuffles all permanents they own into their library, then reveals that many cards from the top of their library. Each player puts all artifact, creature, and land cards revealed this way onto the battlefield, then does the same for enchantment cards, then puts all cards revealed this way that weren't put onto the battlefield on the bottom of their library.

Caves of Koilos

{T}: Add {C}.
{T}: Add {W} or {B}. Caves of Koilos deals 1 damage to you.

Standstill

When a player casts a spell, sacrifice Standstill. If you do, each of that player's opponents draws three cards.

Mana Breach

Whenever a player casts a spell, that player returns a land they control to its owner's hand.

Overburden

Whenever a player puts a nontoken creature onto the battlefield, that player returns a land they control to its owner's hand.

Bloom Tender

{T}: For each color among permanents you control, add one mana of that color.

Storage Matrix

As long as Storage Matrix is untapped, each player chooses artifact, creature, or land during their untap step. That player can untap only permanents of the chosen type this step.

Drannith Magistrate

Your opponents can't cast spells from anywhere other than their hands.

Disrupt Decorum

Goad all creatures you don't control. (Until your next turn, those creatures attack each combat if able and attack a player other than you if able.)

Sylvan Scrying

Search your library for a land card, reveal it, put it into your hand, then shuffle.

Mindslicer

When Mindslicer dies, each player discards their hand.

The Great Aurora

Each player shuffles all cards from their hand and all permanents they own into their library, then draws that many cards. Each player may put any number of land cards from their hand onto the battlefield. Exile The Great Aurora.

Shivan Reef

{T}: Add {C}.
{T}: Add {U} or {R}. Shivan Reef deals 1 damage to you.

Morphic Pool

Morphic Pool enters tapped unless you have two or more opponents.
{T}: Add {U} or {B}.

Curse of the Cabal

Target player sacrifices half the permanents they control of their choice, rounded down.
Suspend 2—{2}{B}{B} (Rather than cast this card from your hand, you may pay {2}{B}{B} and exile it with two 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.)
At the beginning of each player's upkeep, if Curse of the Cabal is suspended, that player may sacrifice a permanent of their choice. If the player does, put two time counters on Curse of the Cabal.

Wheel of Misfortune

Each player secretly chooses a number 0 or greater, then all players reveal those numbers simultaneously and determine the highest and lowest numbers revealed this way. Wheel of Misfortune deals damage equal to the highest number to each player who chose that number. Each player who didn't choose the lowest number discards their hand, then draws seven cards.

Plains

Tainted Remedy

If an opponent would gain life, that player loses that much life instead.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Balancing Act

Each player chooses a number of permanents they control equal to the number of permanents controlled by the player who controls the fewest, then sacrifices the rest. Each player discards cards the same way.

Battlefield Forge

{T}: Add {C}.
{T}: Add {R} or {W}. Battlefield Forge deals 1 damage to you.

Wild Growth

Enchant land
Whenever enchanted land is tapped for mana, its controller adds an additional {G}.

Vault of Champions

Vault of Champions enters tapped unless you have two or more opponents.
{T}: Add {W} or {B}.

Birds of Paradise

Fatespinner

At the beginning of each opponent's upkeep, that player chooses draw step, main phase, or combat phase. The player skips each instance of the chosen step or phase this turn.

Island

Luxury Suite

Luxury Suite enters tapped unless you have two or more opponents.
{T}: Add {B} or {R}.

Sandsteppe Citadel

Sandsteppe Citadel enters tapped.
{T}: Add {W}, {B}, or {G}.

Crumbling Necropolis

Crumbling Necropolis enters tapped.
{T}: Add {U}, {B}, or {R}.

Arcane Signet

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

Balance

Each player chooses a number of lands they control equal to the number of lands controlled by the player who controls the fewest, then sacrifices the rest. Players discard cards and sacrifice creatures the same way.

Chromatic Orrery

You may spend mana as though it were mana of any color.
{T}: Add {C}{C}{C}{C}{C}.
{5}, {T}: Draw a card for each color among permanents you control.

Confusion in the Ranks

Whenever an artifact, creature, or enchantment enters, its controller chooses target permanent another player controls that shares a card type with it. Exchange control of those permanents.

Seaside Citadel

Seaside Citadel enters tapped.
{T}: Add {G}, {W}, or {U}.

Mountain

Karplusan Forest

{T}: Add {C}.
{T}: Add {R} or {G}. Karplusan Forest deals 1 damage to you.

Sol Ring

Apex Observatory

Apex Observatory enters tapped. As it enters, choose a card type shared among two exiled cards used to craft it.
{T}: The next spell you cast this turn of the chosen type can be cast without paying its mana cost.

Eye of Ojer Taq

{T}: Add one mana of any color.
Craft with two that share a card type {6} ({6}, Exile this artifact, Exile the two from among other permanents you control and/or cards from your graveyard: Return this card transformed under its owner's control. Craft only as a sorcery.)

Eye of Ojer Taq // Apex Observatory

Undergrowth Stadium

Undergrowth Stadium enters tapped unless you have two or more opponents.
{T}: Add {B} or {G}.

Rampaging Ferocidon

Menace
Players can't gain life.
Whenever another creature enters, Rampaging Ferocidon deals 1 damage to that creature's controller.

Tempt with Discovery

Tempting offer — Search your library for a land card and put it onto the battlefield. Each opponent may search their library for a land card and put it onto the battlefield. For each opponent who searches a library this way, search your library for a land card and put it onto the battlefield. Then each player who searched a library this way shuffles.

Rampant Growth

Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Command Tower

The Horus Heresy

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — For each opponent, gain control of up to one target nonlegendary creature that player controls for as long as The Horus Heresy remains on the battlefield.
II — Draw a card for each creature you control but don't own.
III — Starting with you, each player chooses a creature. Destroy each creature chosen this way.

Forced Fruition

Whenever an opponent casts a spell, that player draws seven cards.

Sulfurous Springs

{T}: Add {C}.
{T}: Add {B} or {R}. Sulfurous Springs deals 1 damage to you.

Sire of Insanity

At the beginning of each end step, each player discards their hand.

Arboria

Creatures can't attack a player unless that player cast a spell or put a nontoken permanent onto the battlefield during their last turn.

Hall of Gemstone

At the beginning of each player's upkeep, that player chooses a color. Until end of turn, lands tapped for mana produce mana of the chosen color instead of any other color.

Nomad Outpost

Nomad Outpost enters tapped.
{T}: Add {R}, {W}, or {B}.

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Kodama's Reach

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Hive Mind

Whenever a player casts an instant or sorcery spell, each other player copies that spell. Each of those players may choose new targets for their copy.

Relic of Legends

{T}: Add one mana of any color.
Tap an untapped legendary creature you control: Add one mana of any color.

Thieves' Auction

Exile all nontoken permanents. Starting with you, each player chooses one of the exiled cards and puts it onto the battlefield tapped under their control. Repeat this process until all cards exiled this way have been chosen.

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Arcane Sanctum

Arcane Sanctum enters tapped.
{T}: Add {W}, {U}, or {B}.

Pramikon, Sky Rampart

Flying, defender
As Pramikon, Sky Rampart enters, choose left or right.
Each player may attack only the nearest opponent in the chosen direction and planeswalkers controlled by that opponent.

Forest

Commander's Sphere

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

Swamp

Prismatic Omen

Lands you control are every basic land type in addition to their other types.

Omen Machine

Players can't draw cards.
At the beginning of each player's draw step, that player exiles the top card of their library. If it's a land card, the player puts it onto the battlefield. Otherwise, the player casts it without paying its mana cost if able.

Possibility Storm

Whenever a player casts a spell from their hand, that player exiles it, then exiles cards from the top of their library until they exile a card that shares a card type with it. That player may cast that card without paying its mana cost. Then they put all cards exiled with Possibility Storm on the bottom of their library in a random order.

Training Center

Training Center enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Sea of Clouds

Sea of Clouds enters tapped unless you have two or more opponents.
{T}: Add {W} or {U}.

Tide of War

Whenever one or more creatures block, flip a coin. If you win the flip, each blocking creature is sacrificed by its controller. If you lose the flip, each blocked creature is sacrificed by its controller.

Exotic Orchard

Knowledge Pool

Imprint — When Knowledge Pool enters, each player exiles the top three cards of their library.
Whenever a player casts a spell from their hand, that player exiles it. If the player does, they may cast a spell from among other cards exiled with Knowledge Pool without paying its mana cost.

Bonus Round

Until end of turn, whenever a player casts an instant or sorcery spell, that player copies it and may choose new targets for the copy.

Checks and Balances

Cast this spell only if there are three or more players in the game.
Whenever a player casts a spell, each of that player's opponents may discard a card. If they do, counter that spell.

Savage Lands

Savage Lands enters tapped.
{T}: Add {B}, {R}, or {G}.

Mesmeric Orb

Whenever a permanent becomes untapped, that permanent's controller mills a card.

Teferi's Puzzle Box

At the beginning of each player's draw step, that player puts the cards in their hand on the bottom of their library in any order, then draws that many cards.

Scrambleverse

For each nonland permanent, choose a player at random. Then each player gains control of each permanent for which they were chosen. Untap those permanents.

Bountiful Promenade

Bountiful Promenade enters tapped unless you have two or more opponents.
{T}: Add {G} or {W}.

Jungle Shrine

Jungle Shrine enters tapped.
{T}: Add {R}, {G}, or {W}.

Eye of the Storm

Whenever a player casts an instant or sorcery card, exile it. Then that player copies each instant or sorcery card exiled with Eye of the Storm. For each copy, the player may cast the copy without paying its mana cost.

Frontier Bivouac

Frontier Bivouac enters tapped.
{T}: Add {G}, {U}, or {R}.

Opulent Palace

Opulent Palace enters tapped.
{T}: Add {B}, {G}, or {U}.

Jodah, Archmage Eternal

Flying
You may pay {W}{U}{B}{R}{G} rather than pay the mana cost for spells you cast.

Privileged Position

({G/W} can be paid with either {G} or {W}.)
Other permanents you control have hexproof. (They can't be the targets of spells or abilities your opponents control.)

Faeburrow Elder

Vigilance
Faeburrow Elder gets +1/+1 for each color among permanents you control.
{T}: For each color among permanents you control, add one mana of that color.

Boompile

{T}: Flip a coin. If you win the flip, destroy all nonland permanents.

Damnation

Destroy all creatures. They can't be regenerated.

Oppression

Whenever a player casts a spell, that player discards a card.

Imposing Grandeur

Each player may discard their hand and draw cards equal to the greatest mana value of a commander they own on the battlefield or in the command zone.

Grip of Chaos

Whenever a spell or ability is put onto the stack, if it has a single target, reselect its target at random. (Select from among all legal targets.)

Nevinyrral's Disk

Nevinyrral's Disk enters tapped.
{1}, {T}: Destroy all artifacts, creatures, and enchantments.