Thryx, the Sudden Storm

Flash (You may cast this spell any time you could cast an instant.)
Flying
Spells you cast with mana value 5 or greater cost {1} less to cast and can't be countered.

Notion Thief

Flash
If an opponent would draw a card except the first one they draw in each of their draw steps, instead that player skips that draw and you draw a card.

Go for the Throat

Aven Mindcensor

Flash
Flying
If an opponent would search a library, that player searches the top four cards of that library instead.

Lawmage's Binding

Flash
Enchant creature
Enchanted creature can't attack or block, and its activated abilities can't be activated.

Faerie Tauntings

Whenever you cast a spell during an opponent's turn, you may have each opponent lose 1 life.

Stunt Double

Flash
You may have Stunt Double enter as a copy of any creature on the battlefield.

Anguished Unmaking

Exile target nonland permanent. You lose 3 life.

Angel of the Dire Hour

Flash
Flying
When Angel of the Dire Hour enters, if you cast it from your hand, exile all attacking creatures.

Crafty Cutpurse

Flash
When Crafty Cutpurse enters, each token that would be created under an opponent's control this turn is created under your control instead.

Sol Ring

Dreamspoiler Witches

Flying
Whenever you cast a spell during an opponent's turn, you may have target creature get -1/-1 until end of turn.

Mutual Destruction

This spell has flash as long as you control a permanent with flash.
As an additional cost to cast this spell, sacrifice a creature.
Destroy target creature.

Cunning Nightbonder

Flash
Spells with flash you cast cost {1} less to cast and can't be countered.

Spell Queller

Flash
Flying
When Spell Queller enters, exile target spell with mana value 4 or less.
When Spell Queller leaves the battlefield, the exiled card's owner may cast that card without paying its mana cost.

Portal Mage

Flash
When Portal Mage enters during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)

Stinging Lionfish

Whenever you cast your first spell during each opponent's turn, you may tap or untap target nonland permanent.

Voracious Greatshark

Flash (You may cast this spell any time you could cast an instant.)
When this creature enters, counter target artifact or creature spell.

Memory Plunder

You may cast target instant or sorcery card from an opponent's graveyard without paying its mana cost.

Disdainful Stroke

Counter target spell with mana value 4 or greater.

Torrential Gearhulk

Flash
When Torrential Gearhulk enters, you may cast target instant card from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

Raff Capashen, Ship's Mage

Flash
Flying
You may cast historic spells as though they had flash. (Artifacts, legendaries, and Sagas are historic.)

Rewind

Counter target spell. Untap up to four lands.

Leyline of Anticipation

If Leyline of Anticipation is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Orzhov Signet

Arcane Signet

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

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Negate

Mortify

Despark

Exile target permanent with mana value 4 or greater.

Dovin's Veto

This spell can't be countered.
Counter target noncreature spell.

Talisman of Hierarchy

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

Tidal Barracuda

Any player may cast spells as though they had flash.
Your opponents can't cast spells during your turn.

Esper Charm

Choose one —
• Destroy target enchantment.
• Draw two cards.
• Target player discards two cards.

Mystical Teachings

Search your library for an instant card or a card with flash, reveal it, put it into your hand, then shuffle.
Flashback {5}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Glen Elendra Pranksters

Flying
Whenever you cast a spell during an opponent's turn, you may return target creature you control to its owner's hand.

Azorius Signet

Wavebreak Hippocamp

Whenever you cast your first spell during each opponent's turn, draw a card.

Heliod's Intervention

Choose one —
• Destroy X target artifacts and/or enchantments.
• Target player gains twice X life.

Cast Out

Flash
When Cast Out enters, exile target nonland permanent an opponent controls until Cast Out leaves the battlefield.
Cycling {W} ({W}, Discard this card: Draw a card.)

Brineborn Cutthroat

Flash (You may cast this spell any time you could cast an instant.)
Whenever you cast a spell during an opponent's turn, put a +1/+1 counter on this creature.

Chromium, the Mutable

Flash
This spell can't be countered.
Flying
Discard a card: Until end of turn, Chromium, the Mutable becomes a Human with base power and toughness 1/1, loses all abilities, and gains hexproof. It can't be blocked this turn.

Teferi, Mage of Zhalfir

Flash
Creature cards you own that aren't on the battlefield have flash.
Each opponent can cast spells only any time they could cast a sorcery.

Venser, Shaper Savant

Flash (You may cast this spell any time you could cast an instant.)
When Venser, Shaper Savant enters, return target spell or permanent to its owner's hand.

Dimir Signet

Fact or Fiction

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Stonecloaker

Flash
Flying
When Stonecloaker enters, return a creature you control to its owner's hand.
When Stonecloaker enters, exile target card from a graveyard.

Thought Sponge

Flash
Thought Sponge enters with a number of +1/+1 counters on it equal to the greatest number of cards an opponent has drawn this turn.
When Thought Sponge dies, draw cards equal to its power.

Containment Priest

Flash
If a nontoken creature would enter and it wasn't cast, exile it instead.

Slitherwisp

Flash
Whenever you cast another spell that has flash, you draw a card and each opponent loses 1 life.