Mold Adder

Whenever an opponent casts a blue or black spell, you may put a +1/+1 counter on Mold Adder.

Ever-Watching Threshold

Whenever an opponent attacks, if they attacked you and/or a planeswalker you control, draw a card.

Narset's Reversal

Copy target instant or sorcery spell, then return it to its owner's hand. You may choose new targets for the copy.

Voice of Resurgence

Whenever an opponent casts a spell during your turn and when Voice of Resurgence dies, create a green and white Elemental creature token with "This creature's power and toughness are each equal to the number of creatures you control."

Urza's Filter

Multicolored spells cost {2} less to cast.

Kavu Predator

Trample
Whenever an opponent gains life, put that many +1/+1 counters on Kavu Predator.

Dreadhorde Arcanist

Trample
Whenever Dreadhorde Arcanist attacks, you may cast target instant or sorcery card with mana value less than or equal to Dreadhorde Arcanist's power from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.

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.

Citanul Druid

Whenever an opponent casts an artifact spell, put a +1/+1 counter on Citanul Druid.

Lone Wolf of the Natterknolls

Whenever an opponent casts a spell during your turn, draw two cards.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform Lone Wolf of the Natterknolls.

Hermit of the Natterknolls

Whenever an opponent casts a spell during your turn, draw a card.
At the beginning of each upkeep, if no spells were cast last turn, transform Hermit of the Natterknolls.

Hermit of the Natterknolls // Lone Wolf of the Natterknolls

Predatory Hunger

Enchant creature
Whenever an opponent casts a creature spell, put a +1/+1 counter on enchanted creature.

Spellshift

Counter target instant or sorcery spell. Its controller reveals cards from the top of their library until they reveal an instant or sorcery card. That player may cast that card without paying its mana cost. Then the player shuffles.

Taurean Mauler

Changeling (This card is every creature type.)
Whenever an opponent casts a spell, you may put a +1/+1 counter on Taurean Mauler.

Sunscorch Regent

Flying
Whenever an opponent casts a spell, put a +1/+1 counter on Sunscorch Regent and you gain 1 life.

Dualcaster Mage

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

Shell of the Last Kappa

{3}, {T}: Exile target instant or sorcery spell that targets you. (The spell has no effect.)
{3}, {T}, Sacrifice Shell of the Last Kappa: You may cast a spell from among cards exiled with Shell of the Last Kappa without paying its mana cost.

Kynaios and Tiro of Meletis

At the beginning of your end step, draw a card. Each player may put a land card from their hand onto the battlefield, then each opponent who didn't draws a card.

Rule of Law

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

Mangara, the Diplomat

Lifelink
Whenever an opponent attacks with creatures, if two or more of those creatures are attacking you and/or planeswalkers you control, draw a card.
Whenever an opponent casts their second spell each turn, draw a card.

Lurking Predators

Whenever an opponent casts a spell, reveal the top card of your library. If it's a creature card, put it onto the battlefield. Otherwise, you may put that card on the bottom of your library.

Snake Pit

Whenever an opponent casts a blue or black spell, you may create a 1/1 green Snake creature token.

Soldier of the Pantheon

Protection from multicolored
Whenever an opponent casts a multicolored spell, you gain 1 life.

Helm of Awakening

Dragonlair Spider

Reach
Whenever an opponent casts a spell, create a 1/1 green Insect creature token.

Vernal Equinox

Any player may cast creature and enchantment spells as though they had flash.

Cosi's Trickster

Whenever an opponent shuffles their library, you may put a +1/+1 counter on Cosi's Trickster.

Reversal of Fortune

Target opponent reveals their hand. You may copy an instant or sorcery card in it. If you do, you may cast the copy without paying its mana cost.

Tahngarth, First Mate

Tahngarth, First Mate can't be blocked by more than one creature.
Whenever an opponent attacks with one or more creatures, if Tahngarth is tapped, you may have that opponent gain control of Tahngarth until end of combat. If you do, choose a player or planeswalker that opponent is attacking. Tahngarth is attacking that player or planeswalker.

Ishai, Ojutai Dragonspeaker

Flying
Whenever an opponent casts a spell, put a +1/+1 counter on Ishai, Ojutai Dragonspeaker.
Partner (You can have two commanders if both have partner.)

Upwelling

Players don't lose unspent mana as steps and phases end.

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.

Chancellor of the Spires

You may reveal this card from your opening hand. If you do, at the beginning of the first upkeep, each opponent mills seven cards.
Flying
When Chancellor of the Spires enters, you may cast target instant or sorcery card from an opponent's graveyard without paying its mana cost.

Xyris, the Writhing Storm

Flying
Whenever an opponent draws a card except the first one they draw in each of their draw steps, create a 1/1 green Snake creature token.
Whenever Xyris, the Writhing Storm deals combat damage to a player, you and that player each draw that many cards.

Arasta of the Endless Web

Reach
Whenever an opponent casts an instant or sorcery spell, create a 1/2 green Spider creature token with reach.

Chimeric Egg

Whenever an opponent casts a nonartifact spell, put a charge counter on Chimeric Egg.
Remove three charge counters from Chimeric Egg: Chimeric Egg becomes a 6/6 Construct artifact creature with trample until end of turn.

Kraum, Ludevic's Opus

Flying, haste
Whenever an opponent casts their second spell each turn, draw a card.
Partner (You can have two commanders if both have partner.)

Witchstalker

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Whenever an opponent casts a blue or black spell during your turn, put a +1/+1 counter on Witchstalker.

Zurzoth, Chaos Rider

Whenever an opponent draws their first card each turn, if it's not their turn, you create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."
Whenever one or more Devils you control attack one or more players, you and those players each draw a card, then discard a card at random.

Arcane Laboratory

Diluvian Primordial

Flying
When Diluvian Primordial enters, for each opponent, you may cast up to one target instant or sorcery card from that player's graveyard without paying its mana cost. If a spell cast this way would be put into a graveyard, exile it instead.

Aminatou's Augury

Exile the top eight cards of your library. You may put a land card from among them onto the battlefield. Until end of turn, for each nonland card type, you may cast a spell of that type from among the exiled cards without paying its mana cost.

Galvanoth

At the beginning of your upkeep, you may look at the top card of your library. You may cast it without paying its mana cost if it's an instant or sorcery spell.

Infested Roothold

Defender (This creature can't attack.)
Protection from artifacts
Whenever an opponent casts an artifact spell, you may create a 1/1 green Insect creature token.

Arcane Melee

Instant and sorcery spells cost {2} less to cast.

Dirtcowl Wurm

Whenever an opponent plays a land, put a +1/+1 counter on Dirtcowl Wurm.

Insight

Whenever an opponent casts a green spell, you draw a card.

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.

Uyo, Silent Prophet

Flying
{2}, Return two lands you control to their owner's hand: Copy target instant or sorcery spell. You may choose new targets for the copy.

Victory Chimes

Untap Victory Chimes during each other player's untap step.
{T}: A player of your choice adds {C}.

Elite Arcanist

When Elite Arcanist enters, you may exile an instant card from your hand.
{X}, {T}: Copy the exiled card. You may cast the copy without paying its mana cost. X is the mana value of the exiled card.

Eyes of the Wisent

Whenever an opponent casts a blue spell during your turn, you may create a 4/4 green Elemental creature token.