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.

Sudden Substitution

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Exchange control of target noncreature spell and target creature. Then the spell's controller may choose new targets for it.

Selesnya Signet

Orzhov Signet

Atraxa, Grand Unifier

Flying, vigilance, deathtouch, lifelink
When Atraxa, Grand Unifier enters, reveal the top ten cards of your library. For each card type, you may put a card of that type from among the revealed cards into your hand. Put the rest on the bottom of your library in a random order. (Artifact, battle, creature, enchantment, instant, land, planeswalker, and sorcery are card types.)

Perplexing Chimera

Whenever an opponent casts a spell, you may exchange control of Perplexing Chimera and that spell. If you do, you may choose new targets for the spell. (If the spell becomes a permanent, you control that permanent.)

Propaganda

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

Modify Memory

Exchange control of two target creatures controlled by different players. If you control neither creature, draw three cards.

Shared Fate

If a player would draw a card, that player exiles the top card of one of their opponents' libraries face down instead.
Each player may look at cards they exiled with Shared Fate, and they may play lands and cast spells from among those cards.

Curse of Echoes

Enchant player
Whenever enchanted player casts an instant or sorcery spell, each other player may copy that spell and may choose new targets for the copy they control.

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.

Avarice Totem

{5}: Exchange control of Avarice Totem and target nonland permanent.

Thought Vessel

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

Rhystic Study

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

Arcane Signet

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

Gilded Drake

Flying
When Gilded Drake enters, exchange control of Gilded Drake and up to one target creature an opponent controls. If you don't or can't make an exchange, sacrifice Gilded Drake. This ability still resolves if its target becomes illegal.

Simic Signet

Dimir Signet

Puca's Mischief

At the beginning of your upkeep, you may exchange control of target nonland permanent you control and target nonland permanent an opponent controls with equal or lesser mana value.

Azorius Signet

Mind Stone

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

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.

Golgari Signet

Sol Ring

Mirage Mirror

{2}: Mirage Mirror becomes a copy of target artifact, creature, enchantment, or land until end of turn.

Wave of Vitriol

Each player sacrifices all artifacts, enchantments, and nonbasic lands they control. For each land sacrificed this way, its controller may search their library for a basic land card and put it onto the battlefield tapped. Then each player who searched their library this way shuffles.

Timesifter

At the beginning of each upkeep, each player exiles the top card of their library. The player who exiled the card with the highest mana value takes an extra turn after this one. If two or more players' cards are tied for highest, the tied players repeat this process until the tie is broken.

Djinn of Infinite Deceits

Flying
{T}: Exchange control of two target nonlegendary creatures. You can't activate this ability during combat.