Mirror March

Whenever a nontoken creature enters the battlefield under your control, flip a coin until you lose a flip. For each flip you won, create a token that's a copy of that creature. Those tokens gain haste. Exile them at the beginning of the next end step.

Chromatic Lantern

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

Bloom Tender

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

Fieldmist Borderpost

You may pay {1} and return a basic land you control to its owner's hand rather than pay this spell's mana cost.
Fieldmist Borderpost enters the battlefield tapped.
{T}: Add {W} or {U}.

Wildfield Borderpost

You may pay {1} and return a basic land you control to its owner's hand rather than pay this spell's mana cost.
Wildfield Borderpost enters the battlefield tapped.
{T}: Add {G} or {W}.

Sol Ring

Firewild Borderpost

You may pay {1} and return a basic land you control to its owner's hand rather than pay this spell's mana cost.
Firewild Borderpost enters the battlefield tapped.
{T}: Add {R} or {G}.

Conflux

Search your library for a white card, a blue card, a black card, a red card, and a green card. Reveal those cards, put them into your hand, then shuffle.

Izzet Signet

Lich's Mirror

If you would lose the game, instead shuffle your hand, your graveyard, and all permanents you own into your library, then draw seven cards and your life total becomes 20.

Rule of Law

Each player can't cast more than one spell each turn.

Orzhov Signet

Door to Nothingness

Door to Nothingness enters the battlefield tapped.
{W}{W}{U}{U}{B}{B}{R}{R}{G}{G}, {T}, Sacrifice Door to Nothingness: Target player loses the game.

Arcane Signet

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

Boros Signet

Golgari Signet

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.

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.

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Karn Liberated

+4: Target player exiles a card from their hand.
−3: Exile target permanent.
−14: Restart the game, leaving in exile all non-Aura permanent cards exiled with Karn Liberated. Then put those cards onto the battlefield under your control.

The Magic Mirror

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.
You have no maximum hand size.
At the beginning of your upkeep, put a knowledge counter on The Magic Mirror, then draw a card for each knowledge counter on The Magic Mirror.

Knowledge Pool

Imprint — When Knowledge Pool enters the battlefield, 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.

Thought Vessel

Ramos, Dragon Engine

Flying
Whenever you cast a spell, put a +1/+1 counter on Ramos, Dragon Engine for each of that spell's colors.
Remove five +1/+1 counters from Ramos: Add {W}{W}{U}{U}{B}{B}{R}{R}{G}{G}. Activate only once each turn.

Goblin Game

Each player hides at least one item, then all players reveal them simultaneously. Each player loses life equal to the number of items they revealed. The player who revealed the fewest items then loses half their life, rounded up. If two or more players are tied for fewest, each loses half their life, rounded up.

Venser's Journal

You have no maximum hand size.
At the beginning of your upkeep, you gain 1 life for each card in your hand.

Game of Chaos

Flip a coin. If you win the flip, you gain 1 life and target opponent loses 1 life, and you decide whether to flip again. If you lose the flip, you lose 1 life and that opponent gains 1 life, and that player decides whether to flip again. Double the life stakes with each flip.

Veinfire Borderpost

You may pay {1} and return a basic land you control to its owner's hand rather than pay this spell's mana cost.
Veinfire Borderpost enters the battlefield tapped.
{T}: Add {B} or {R}.

Mistvein Borderpost

You may pay {1} and return a basic land you control to its owner's hand rather than pay this spell's mana cost.
Mistvein Borderpost enters the battlefield tapped.
{T}: Add {U} or {B}.

Mirror Sheen

{1}{U/R}{U/R}: Copy target instant or sorcery spell that targets you. You may choose new targets for the copy.

Mirror Universe

{T}, Sacrifice Mirror Universe: Exchange life totals with target opponent. Activate only during your upkeep.