Ishai, Ojutai Dragonspeaker

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

Chancellor of the Annex

You may reveal this card from your opening hand. If you do, when each opponent casts their first spell of the game, counter that spell unless that player pays {1}.
Flying
Whenever an opponent casts a spell, counter it unless that player pays {1}.

Ivy, Gleeful Spellthief

Flying
Whenever a player casts a spell that targets only a single creature other than Ivy, you may copy that spell. The copy targets Ivy. (A copy of an Aura spell becomes a token.)

Dragonlair Spider

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

Kambal, Consul of Allocation

Whenever an opponent casts a noncreature spell, that player loses 2 life and you gain 2 life.

Crumbling Necropolis

This land enters tapped.
{T}: Add {U}, {B}, or {R}.

Forgotten Ancient

Whenever a player casts a spell, you may put a +1/+1 counter on this creature.
At the beginning of your upkeep, you may move any number of +1/+1 counters from this creature onto other creatures.

Memory Erosion

Whenever an opponent casts a spell, that player mills two cards.

Savage Lands

This land enters tapped.
{T}: Add {B}, {R}, or {G}.

Counterbalance

Whenever an opponent casts a spell, you may reveal the top card of your library. If you do, counter that spell if it has the same mana value as the revealed card.

Mystic Monastery

This land enters tapped.
{T}: Add {U}, {R}, or {W}.

Plains

Mana Breach

Whenever a player casts a spell, that player returns a land they control to its owner's hand.

Golem's Heart

Whenever a player casts an artifact spell, you may gain 1 life.

Swindler's Scheme

Whenever an opponent casts a spell from their hand, you may reveal the top card of your library. If it shares a card type with that spell, counter that spell and that opponent may cast the revealed card without paying its mana cost.

Cindervines

Whenever an opponent casts a noncreature spell, this enchantment deals 1 damage to that player.
{1}, Sacrifice this enchantment: Destroy target artifact or enchantment. This enchantment deals 2 damage to that permanent's controller.

Pure Reflection

Whenever a player casts a creature spell, destroy all Reflections. Then that player creates an X/X white Reflection creature token, where X is the mana value of that spell.

Command Tower

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

Glademuse

Whenever a player casts a spell, if it's not their turn, that player draws a card.

Hunting Grounds

Threshold — As long as there are seven or more cards in your graveyard, this enchantment has "Whenever an opponent casts a spell, you may put a creature card from your hand onto the battlefield."

Painful Quandary

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.

Indatha Triome

({T}: Add {W}, {B}, or {G}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Ziatora's Proving Ground

({T}: Add {B}, {R}, or {G}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Soot Imp

Flying
Whenever a player casts a nonblack spell, that player loses 1 life.

Perplexing Chimera

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

Soul Barrier

Whenever an opponent casts a creature spell, this enchantment deals 2 damage to that player unless they pay {2}.

Raugrin Triome

({T}: Add {U}, {R}, or {W}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Drooling Ogre

Whenever a player casts an artifact spell, that player gains control of this creature. (This effect lasts indefinitely.)

Forest

Taurean Mauler

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

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.

Rod of Absorption

Whenever a player casts an instant or sorcery spell, exile it instead of putting it into a graveyard as it resolves.
{X}, {T}, Sacrifice this artifact: You may cast any number of spells from among cards exiled with this artifact with total mana value X or less without paying their mana costs.

Breeding Pool

({T}: Add {G} or {U}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Managorger Hydra

Trample
Whenever a player casts a spell, put a +1/+1 counter on this creature.

Geometric Nexus

Whenever a player casts an instant or sorcery spell, put a number of charge counters on this artifact equal to that spell's mana value.
{6}, {T}, Remove all charge counters from this artifact: Create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it, where X is the number of charge counters removed this way.

Stomping Ground

({T}: Add {R} or {G}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Raffine's Tower

({T}: Add {W}, {U}, or {B}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Island

Explore the Vastlands

Each player looks at the top five cards of their library and may reveal a land card and/or an instant or sorcery card from among them. Each player puts the cards they revealed this way into their hand and the rest on the bottom of their library in a random order. Each player gains 3 life.

Wandering Archaic

Whenever an opponent casts an instant or sorcery spell, they may pay {2}. If they don't, you may copy that spell. You may choose new targets for the copy.

Wandering Archaic // Explore the Vastlands

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 this enchantment on the bottom of their library in a random order.

Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Kaervek the Merciless

Whenever an opponent casts a spell, Kaervek deals damage equal to that spell's mana value to any target.

Eidolon of the Great Revel

Whenever a player casts a spell with mana value 3 or less, this creature deals 2 damage to that player.

Zagoth Triome

({T}: Add {B}, {G}, or {U}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Opulent Palace

This land enters tapped.
{T}: Add {B}, {G}, or {U}.

Reparations

Whenever an opponent casts a spell that targets you or a creature you control, you may draw a card.

Savai Triome

({T}: Add {R}, {W}, or {B}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

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 this creature.

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 this creature.

Hermit of the Natterknolls // Lone Wolf of the Natterknolls

Lavinia, Azorius Renegade

Each opponent can't cast noncreature spells with mana value greater than the number of lands that player controls.
Whenever an opponent casts a spell, if no mana was spent to cast it, counter that spell.

Rug of Smothering

Flying
Whenever a player casts a spell, they lose 1 life for each spell they've cast this turn.

Captured by the Consulate

Enchant creature you don't control
Enchanted creature can't attack.
Whenever an opponent casts a spell, if it has a single target, change the target to enchanted creature if able.

Decree of Silence

Whenever an opponent casts a spell, counter that spell and put a depletion counter on this enchantment. If there are three or more depletion counters on this enchantment, sacrifice it.
Cycling {4}{U}{U} ({4}{U}{U}, Discard this card: Draw a card.)
When you cycle this card, you may counter target spell.

Steam Vents

({T}: Add {U} or {R}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Liesa, Shroud of Dusk

Rather than pay {2} for each previous time you've cast this spell from the command zone this game, pay 2 life that many times.
Flying, lifelink
Whenever a player casts a spell, they lose 2 life.

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.

Aether Sting

Whenever an opponent casts a creature spell, this enchantment deals 1 damage to that player.

Noosegraf Mob

This creature enters with five +1/+1 counters on it.
Whenever a player casts a spell, remove a +1/+1 counter from this creature. If you do, create a 2/2 black Zombie creature token.

Tovolar's Magehunter

Whenever an opponent casts a spell, this creature deals 2 damage to that player.
At the beginning of each upkeep, if a player cast two or more spells last turn, transform this creature.

Mondronen Shaman

At the beginning of each upkeep, if no spells were cast last turn, transform this creature.

Mondronen Shaman // Tovolar's Magehunter

Void Mirror

Whenever a player casts a spell, if no colored mana was spent to cast it, counter that spell.

Ketria Triome

({T}: Add {G}, {U}, or {R}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Jegantha, the Wellspring

Companion — No card in your starting deck has more than one of the same mana symbol in its mana cost. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
{T}: Add {W}{U}{B}{R}{G}. This mana can't be spent to pay generic mana costs.

Pyrostatic Pillar

Whenever a player casts a spell with mana value 3 or less, this enchantment deals 2 damage to that player.

Rhystic Study

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

Reflecting Pool

{T}: Add one mana of any type that a land you control could produce.

Thundering Mightmare

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Thundering Mightmare is paired with another creature, each of those creatures has "Whenever an opponent casts a spell, put a +1/+1 counter on this creature."

Forced Fruition

Whenever an opponent casts a spell, that player draws seven cards.

Spelltithe Enforcer

Whenever an opponent casts a spell, that player sacrifices a permanent of their choice unless they pay {1}.

Ghostly Pilferer

Whenever this creature becomes untapped, you may pay {2}. If you do, draw a card.
Whenever an opponent casts a spell from anywhere other than their hand, draw a card.
Discard a card: This creature can't be blocked this turn.

Predatory Hunger

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

Isolation Cell

Whenever an opponent casts a creature spell, that player loses 2 life unless they pay {2}.

Curse of Wizardry

As this enchantment enters, choose a color.
Whenever a player casts a spell of the chosen color, that player loses 1 life.

Unifying Theory

Whenever a player casts a spell, that player may pay {2}. If the player does, they draw a card.

Seaside Citadel

This land enters tapped.
{T}: Add {G}, {W}, or {U}.

Jungle Shrine

This land enters tapped.
{T}: Add {R}, {G}, or {W}.

Hallowed Fountain

({T}: Add {W} or {U}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Nezahal, Primal Tide

This spell can't be countered.
You have no maximum hand size.
Whenever an opponent casts a noncreature spell, draw a card.
Discard three cards: Exile Nezahal. Return it to the battlefield tapped under its owner's control at the beginning of the next end step.

Xander's Lounge

({T}: Add {U}, {B}, or {R}.)
This land enters tapped.
Cycling {3} ({3}, Discard this card: Draw a 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.

Roiling Vortex

At the beginning of each player's upkeep, this enchantment deals 1 damage to them.
Whenever a player casts a spell, if no mana was spent to cast that spell, this enchantment deals 5 damage to that player.
{R}: Your opponents can't gain life this turn.

Frontier Bivouac

This land enters tapped.
{T}: Add {G}, {U}, or {R}.

Overgrown Tomb

({T}: Add {B} or {G}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Heartwood Storyteller

Whenever a player casts a noncreature spell, each of that player's opponents may draw a card.

Ruric Thar, the Unbowed

Vigilance, reach
Ruric Thar attacks each combat if able.
Whenever a player casts a noncreature spell, Ruric Thar deals 6 damage to that player.

Ash Zealot

First strike, haste
Whenever a player casts a spell from a graveyard, this creature deals 3 damage to that player.

Bloodvial Purveyor

Flying, trample
Whenever an opponent casts a spell, that player creates a Blood token. (It's an artifact with "{1}, {T}, Discard a card, Sacrifice this token: Draw a card.")
Whenever this creature attacks, it gets +1/+0 until end of turn for each Blood token defending player controls.

Dovescape

({W/U} can be paid with either {W} or {U}.)
Whenever a player casts a noncreature spell, counter that spell. That player creates X 1/1 white and blue Bird creature tokens with flying, where X is the spell's mana value.

Mountain

Sacred Foundry

({T}: Add {R} or {W}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Mogg Sentry

Whenever an opponent casts a spell, this creature gets +2/+2 until end of turn.

Temple Garden

({T}: Add {G} or {W}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Sunscorch Regent

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

Swamp

Sandsteppe Citadel

This land enters tapped.
{T}: Add {W}, {B}, or {G}.

Spellshock

Whenever a player casts a spell, this enchantment deals 2 damage to that player.

Mystic Remora

Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
Whenever an opponent casts a noncreature spell, you may draw a card unless that player pays {4}.

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.

Godless Shrine

({T}: Add {W} or {B}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.