Trouble in Pairs

If an opponent would begin an extra turn, that player skips that turn instead.
Whenever an opponent attacks you with two or more creatures, draws their second card each turn, or casts their second spell each turn, you draw a card.

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.

Sauron, the Dark Lord

Ward—Sacrifice a legendary artifact or legendary creature.
Whenever an opponent casts a spell, amass Orcs 1.
Whenever an Army you control deals combat damage to a player, the Ring tempts you.
Whenever the Ring tempts you, you may discard your hand. If you do, draw four cards.

Rejuvenating Springs

Rejuvenating Springs enters the battlefield tapped unless you have two or more opponents.
{T}: Add {G} or {U}.

Breeding Pool

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

Confessor

Whenever a player discards a card, you may gain 1 life.

Zenith Chronicler

Whenever a player casts their first multicolored spell each turn, each other player draws a card.

Fire-Lit Thicket

{T}: Add {C}.
{R/G}, {T}: Add {R}{R}, {R}{G}, or {G}{G}.

Spire Garden

Spire Garden enters the battlefield tapped unless you have two or more opponents.
{T}: Add {R} or {G}.

Memory Erosion

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

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}.

Wooded Bastion

{T}: Add {C}.
{G/W}, {T}: Add {G}{G}, {G}{W}, or {W}{W}.

Arid Mesa

{T}, Pay 1 life, Sacrifice Arid Mesa: Search your library for a Mountain or Plains card, put it onto the battlefield, then shuffle.

Ziatora's Proving Ground

({T}: Add {B}, {R}, or {G}.)
Ziatora's Proving Ground enters the battlefield tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Kambal, Consul of Allocation

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

Howling Moon

At the beginning of combat on your turn, target Wolf or Werewolf you control gets +2/+2 until end of turn.
Whenever an opponent casts their second spell each turn, create a 2/2 green Wolf creature token.

Path of Ancestry

Path of Ancestry enters the battlefield tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Bloodchief Ascension

At the beginning of each end step, if an opponent lost 2 or more life this turn, you may put a quest counter on Bloodchief Ascension. (Damage causes loss of life.)
Whenever a card is put into an opponent's graveyard from anywhere, if Bloodchief Ascension has three or more quest counters on it, you may have that player lose 2 life. If you do, you gain 2 life.

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.

Thundering Mightmare

Soulbond (You may pair this creature with another unpaired creature when either enters the battlefield. 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."

Soldier of the Pantheon

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

Insight

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

Soot Imp

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

Bountiful Promenade

Bountiful Promenade enters the battlefield tapped unless you have two or more opponents.
{T}: Add {G} or {W}.

Vault of Champions

Vault of Champions enters the battlefield tapped unless you have two or more opponents.
{T}: Add {W} or {B}.

Hunting Grounds

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

Rhystic Study

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

Mage Hunter

Whenever an opponent casts or copies an instant or sorcery spell, they lose 1 life.

Plains

Forest

Treasure Nabber

Whenever an opponent taps an artifact for mana, gain control of that artifact until the end of your next turn.

Windswept Heath

{T}, Pay 1 life, Sacrifice Windswept Heath: Search your library for a Forest or Plains card, put it onto the battlefield, then shuffle.

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.

Ghostly Pilferer

Whenever Ghostly Pilferer 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: Ghostly Pilferer can't be blocked this turn.

Wedding Ring

When Wedding Ring enters the battlefield, if it was cast, target opponent creates a token that's a copy of it.
Whenever an opponent who controls an artifact named Wedding Ring draws a card during their turn, you draw a card.
Whenever an opponent who controls an artifact named Wedding Ring gains life during their turn, you gain that much life.

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.)

Spectator Seating

Spectator Seating enters the battlefield tapped unless you have two or more opponents.
{T}: Add {R} or {W}.

Monologue Tax

Whenever an opponent casts their second spell each turn, you create a Treasure token.

Dragonlair Spider

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

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Forgotten Ancient

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

Exotic Orchard

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

Orcish Bowmasters

Flash
When Orcish Bowmasters enters the battlefield and whenever an opponent draws a card except the first one they draw in each of their draw steps, Orcish Bowmasters deals 1 damage to any target. Then amass Orcs 1.

Jin-Gitaxias, Progress Tyrant

Whenever you cast an artifact, instant, or sorcery spell, copy that spell. You may choose new targets for the copy. This ability triggers only once each turn. (A copy of a permanent spell becomes a token.)
Whenever an opponent casts an artifact, instant, or sorcery spell, counter that spell. This ability triggers only once each turn.

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 artifact: Draw a card.")
Whenever Bloodvial Purveyor attacks, it gets +1/+0 until end of turn for each Blood token defending player controls.

Mayhem Devil

Whenever a player sacrifices a permanent, Mayhem Devil deals 1 damage to any target.

The Council of Four

Whenever a player draws their second card during their turn, you draw a card.
Whenever a player casts their second spell during their turn, you create a 2/2 white Knight creature token.

Mountain

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.

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.

Consecrated Sphinx

Flying
Whenever an opponent draws a card, you may draw two cards.

Sea of Clouds

Sea of Clouds enters the battlefield tapped unless you have two or more opponents.
{T}: Add {W} or {U}.

Talion, the Kindly Lord

Flying
As Talion, the Kindly Lord enters the battlefield, choose a number between 1 and 10.
Whenever an opponent casts a spell with mana value, power, or toughness equal to the chosen number, that player loses 2 life and you draw a card.

Sunken Ruins

{T}: Add {C}.
{U/B}, {T}: Add {U}{U}, {U}{B}, or {B}{B}.

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.

Graven Cairns

{T}: Add {C}.
{B/R}, {T}: Add {B}{B}, {B}{R}, or {R}{R}.

The World Tree

The World Tree enters the battlefield tapped.
{T}: Add {G}.
As long as you control six or more lands, lands you control have "{T}: Add one mana of any color."
{W}{W}{U}{U}{B}{B}{R}{R}{G}{G}, {T}, Sacrifice The World Tree: Search your library for any number of God cards, put them onto the battlefield, then shuffle.

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.

Mind's Dilation

Whenever an opponent casts their first spell each turn, that player exiles the top card of their library. If it's a nonland card, you may cast it without paying its mana cost.

Godless Shrine

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

Heartwood Storyteller

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

Suture Priest

Whenever another creature enters the battlefield under your control, you may gain 1 life.
Whenever a creature enters the battlefield under an opponent's control, you may have that player lose 1 life.

Command Tower

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

Cemetery Gatekeeper

First strike
When Cemetery Gatekeeper enters the battlefield, exile a card from a graveyard.
Whenever a player plays a land or casts a spell, if it shares a card type with the exiled card, Cemetery Gatekeeper deals 2 damage to that player.

Undergrowth Stadium

Undergrowth Stadium enters the battlefield tapped unless you have two or more opponents.
{T}: Add {B} or {G}.

Deep-Sea Kraken

Deep-Sea Kraken can't be blocked.
Suspend 9—{2}{U} (Rather than cast this card from your hand, you may pay {2}{U} and exile it with nine time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)
Whenever an opponent casts a spell, if Deep-Sea Kraken is suspended, remove a time counter from it.

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.

Swamp

Scalding Tarn

{T}, Pay 1 life, Sacrifice Scalding Tarn: Search your library for an Island or Mountain card, put it onto the battlefield, then shuffle.

Xander's Lounge

({T}: Add {U}, {B}, or {R}.)
Xander's Lounge enters the battlefield tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Cindervines

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

Luxury Suite

Luxury Suite enters the battlefield tapped unless you have two or more opponents.
{T}: Add {B} or {R}.

Managorger Hydra

Trample
Whenever a player casts a spell, put a +1/+1 counter on Managorger Hydra.

Marsh Flats

{T}, Pay 1 life, Sacrifice Marsh Flats: Search your library for a Plains or Swamp card, put it onto the battlefield, then shuffle.

Jetmir's Garden

({T}: Add {R}, {G}, or {W}.)
Jetmir's Garden enters the battlefield tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Raffine's Tower

({T}: Add {W}, {U}, or {B}.)
Raffine's Tower enters the battlefield tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Glademuse

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

Ledger Shredder

Flying
Whenever a player casts their second spell each turn, Ledger Shredder connives. (Draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on this creature.)

Primal Surge

Exile the top card of your library. If it's a permanent card, you may put it onto the battlefield. If you do, repeat this process.

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.

Island

Lotho, Corrupt Shirriff

Whenever a player casts their second spell each turn, you lose 1 life and create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Morphic Pool

Morphic Pool enters the battlefield tapped unless you have two or more opponents.
{T}: Add {U} or {B}.

Sacred Foundry

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

Spara's Headquarters

({T}: Add {G}, {W}, or {U}.)
Spara's Headquarters enters the battlefield tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Training Center

Training Center enters the battlefield tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Paradise Plume

As Paradise Plume enters the battlefield, choose a color.
Whenever a player casts a spell of the chosen color, you may gain 1 life.
{T}: Add one mana of the chosen color.

Faerie Mastermind

Flash
Flying
Whenever an opponent draws their second card each turn, you draw a card.
{3}{U}: Each player draws a card.

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.

Rug of Smothering

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

Sunscorch Regent

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

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.)

Stomping Ground

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

Mystic Gate

{T}: Add {C}.
{W/U}, {T}: Add {W}{W}, {W}{U}, or {U}{U}.

Steam Vents

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

Psychic Surgery

Whenever an opponent shuffles their library, you may look at the top two cards of that library. You may exile one of those cards. Then put the rest on top of that library in any order.

Jolene, the Plunder Queen

Whenever a player attacks one or more of your opponents, that attacking player creates a Treasure token.
If you would create one or more Treasure tokens, instead create those tokens plus an additional Treasure token.
Sacrifice five Treasures: Put five +1/+1 counters on Jolene.

Esper Sentinel

Whenever an opponent casts their first noncreature spell each turn, draw a card unless that player pays {X}, where X is Esper Sentinel's power.

Archivist of Oghma

Flash
Whenever an opponent searches their library, you gain 1 life and draw a card.

Karona, False God

Haste
At the beginning of each player's upkeep, that player untaps Karona, False God and gains control of it.
Whenever Karona attacks, creatures of the creature type of your choice get +3/+3 until end of turn.