Negate

Pain Distributor

Menace
Whenever a player casts their first spell each turn, they create a Treasure token.
Whenever an artifact an opponent controls is put into a graveyard from the battlefield, Pain Distributor deals 1 damage to that player.

Krosan Grip

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Destroy target artifact or enchantment.

Frilled Mystic

Flash
When Frilled Mystic enters, you may counter target spell.

Wavebreak Hippocamp

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

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.

Hullbreaker Horror

Flash
This spell can't be countered.
Whenever you cast a spell, choose up to one —
• Return target spell you don't control to its owner's hand.
• Return target nonland permanent to its owner's hand.

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.

Reality Shift

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)

Rodeo Pyromancers

Whenever you cast your first spell each turn, add {R}{R}.

Worldly Tutor

Search your library for a creature card, reveal it, then shuffle and put the card on top.

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Swan Song

Counter target enchantment, instant, or sorcery spell. Its controller creates a 2/2 blue Bird creature token with flying.

Rashmi, Eternities Crafter

Whenever you cast your first spell each turn, reveal the top card of your library. You may cast it without paying its mana cost if it's a spell with lesser mana value. If you don't cast it, put it into your hand.

Deflecting Swat

If you control a commander, you may cast this spell without paying its mana cost.
You may choose new targets for target spell or ability.

Stinging Lionfish

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

Shadow in the Warp

The first creature spell you cast each turn costs {2} less to cast.
Whenever an opponent casts their first noncreature spell each turn, Shadow in the Warp deals 2 damage to that player.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Stunt Double

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

Three Visits

Search your library for a Forest card, put it onto the battlefield, then shuffle.

Fierce Guardianship

If you control a commander, you may cast this spell without paying its mana cost.
Counter target noncreature spell.

Snapcaster Mage

Flash
When Snapcaster Mage enters, target instant or sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost. (You may cast that card from your graveyard for its flashback cost. Then exile it.)

Alania, Divergent Storm

Whenever you cast a spell, if it's the first instant spell, the first sorcery spell, or the first Otter spell other than Alania you've cast this turn, you may have target opponent draw a card. If you do, copy that spell. You may choose new targets for the copy.

Wilderness Reclamation

At the beginning of your end step, untap all lands you control.

Visions of Beyond

Draw a card. If a graveyard has twenty or more cards in it, draw three cards instead.

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Dualcaster Mage

Flash
When Dualcaster Mage enters, copy target instant or sorcery spell. You may choose new targets for the copy.

Seedborn Muse

Untap all permanents you control during each other player's untap step.

Mystic Snake

Flash
When Mystic Snake enters, counter target spell.

An Offer You Can't Refuse

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Sword of Once and Future

Equipped creature gets +2/+2 and has protection from blue and from black.
Whenever equipped creature deals combat damage to a player, surveil 2. Then you may cast an instant or sorcery spell with mana value 2 or less from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.
Equip {2}

The Twelfth Doctor

The first spell you cast from anywhere other than your hand each turn has demonstrate. (When you cast that spell, you may copy it. If you do, choose an opponent to also copy it. A copy of a permanent spell becomes a token.)
Whenever you copy a spell, put a +1/+1 counter on The Twelfth Doctor.

Surrak Dragonclaw

Flash
This spell can't be countered.
Creature spells you control can't be countered.
Other creatures you control have trample.

Pull from Tomorrow

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Green Slime

Flash
When Green Slime enters, counter target activated or triggered ability from an artifact or enchantment source. If a permanent's ability is countered this way, destroy that permanent.
Foretell {G} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Double Vision

Whenever you cast your first instant or sorcery spell each turn, copy that spell. You may choose new targets for the copy.

Nature's Claim

Destroy target artifact or enchantment. Its controller gains 4 life.

Brainstorm

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

Baral and Kari Zev

First strike, menace
Whenever you cast your first instant or sorcery spell each turn, you may cast a spell with lesser mana value that shares a card type with it from your hand without paying its mana cost. If you don't, create First Mate Ragavan, a legendary 2/1 red Monkey Pirate creature token. It gains haste until end of turn.

Wizards of Thay

Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Instant and sorcery spells you cast cost {1} less to cast.
You may cast sorcery spells as though they had flash.

Return of the Wildspeaker

Choose one —
• Draw cards equal to the greatest power among non-Human creatures you control.
• Non-Human creatures you control get +3/+3 until end of turn.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Keep Watch

Arcane Bombardment

Whenever you cast your first instant or sorcery spell each turn, exile an instant or sorcery card at random from your graveyard. Then copy each card exiled with Arcane Bombardment. You may cast any number of the copies without paying their mana costs.