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.)

Exotic Orchard

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

Godless Shrine

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

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.

Isolation Cell

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

Forest

Talion, the Kindly Lord

Flying
As Talion, the Kindly Lord enters, 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.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Undergrowth Stadium

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

Deadly Rollick

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

Faerie Mastermind

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

Mirror Shield

Equipped creature gets +0/+2 and has hexproof and "Whenever a creature with deathtouch blocks or becomes blocked by this creature, destroy that creature."
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Painful Quandary

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

Bountiful Promenade

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

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.

Talisman of Resilience

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

Damn

Destroy target creature. A creature destroyed this way can't be regenerated.
Overload {2}{W}{W} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Champion's Helm

Equipped creature gets +2/+2.
As long as equipped creature is legendary, it has hexproof. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Dreamroot Cascade

Dreamroot Cascade enters tapped unless you control two or more other lands.
{T}: Add {G} or {U}.

Dispel

Muddle the Mixture

Counter target instant or sorcery spell.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Sea of Clouds

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

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

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."

Deathcap Glade

Deathcap Glade enters tapped unless you control two or more other lands.
{T}: Add {B} or {G}.

Flooded Strand

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

Forced Fruition

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

Kambal, Consul of Allocation

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

Archivist of Oghma

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

Misty Rainforest

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

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

Whispersilk Cloak

Equipped creature can't be blocked and has shroud. (It can't be the target of spells or abilities.)
Equip {2}

Temple Garden

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

Runic Armasaur

Whenever an opponent activates an ability of a creature or land that isn't a mana ability, you may draw a card.

Bold Plagiarist

Flash
Whenever an opponent puts one or more counters on a creature they control, they put the same number and kind of counters on Bold Plagiarist.

Rhystic Study

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

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, Primal Tide. Return it to the battlefield tapped under its owner's control at the beginning of the next end step.

Cyclonic Rift

Return target nonland permanent you don't control to its owner's hand.
Overload {6}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

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."

Arcane Signet

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

Talisman of Progress

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

Overgrown Farmland

Overgrown Farmland enters tapped unless you control two or more other lands.
{T}: Add {G} or {W}.

Polluted Delta

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

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.

Talisman of Dominance

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

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.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Sunscorch Regent

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

Brushland

{T}: Add {C}.
{T}: Add {G} or {W}. Brushland deals 1 damage to you.

Springleaf Drum

{T}, Tap an untapped creature you control: Add one mana of any color.

Verdant Catacombs

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

Ever-Watching Threshold

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

Rejuvenating Springs

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

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.")

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}.

Into the Flood Maw

Gift a tapped Fish (You may promise an opponent a gift as you cast this spell. If you do, they create a tapped 1/1 blue Fish creature token before its other effects.)
Return target creature an opponent controls to its owner's hand. If the gift was promised, instead return target nonland permanent an opponent controls to its owner's hand.

Fellwar Stone

Hallowed Fountain

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

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Island

Plains

Llanowar Wastes

{T}: Add {C}.
{T}: Add {B} or {G}. Llanowar Wastes deals 1 damage to you.

Teferi's Protection

Until your next turn, your life total can't change and you gain protection from everything. All permanents you control phase out. (While they're phased out, they're treated as though they don't exist. They phase in before you untap during your untap step.)
Exile Teferi's Protection.

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.

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.

Assassin's Trophy

Destroy target permanent an opponent controls. Its controller may search their library for a basic land card, put it onto the battlefield, then shuffle.

Reyhan, Last of the Abzan

Reyhan, Last of the Abzan enters with three +1/+1 counters on it.
Whenever a creature you control dies or is put into the command zone, if it had one or more +1/+1 counters on it, you may put that many +1/+1 counters on target creature.
Partner (You can have two commanders if both have partner.)

Counterspell

Adarkar Wastes

{T}: Add {C}.
{T}: Add {W} or {U}. Adarkar Wastes deals 1 damage to you.

Command Tower

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.

Mage Hunter

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

Strix Serenade

Counter target artifact, creature, or planeswalker spell. Its controller creates a 2/2 blue Bird creature token with flying.

Deserted Beach

Deserted Beach enters tapped unless you control two or more other lands.
{T}: Add {W} or {U}.

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

Nature's Claim

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

Sheoldred, the Apocalypse

Deathtouch
Whenever you draw a card, you gain 2 life.
Whenever an opponent draws a card, they lose 2 life.

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.

Morphic Pool

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

Breeding Pool

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

Shattered Sanctum

Shattered Sanctum enters tapped unless you control two or more other lands.
{T}: Add {W} or {B}.

Underground River

{T}: Add {C}.
{T}: Add {U} or {B}. Underground River deals 1 damage to you.

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.

Caves of Koilos

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

Monologue Tax

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

Dovin's Veto

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

Fate Unraveler

Whenever an opponent draws a card, Fate Unraveler deals 1 damage to that player.

Overgrown Tomb

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

Underworld Dreams

Whenever an opponent draws a card, Underworld Dreams deals 1 damage to that player.

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.

Toxic Deluge

As an additional cost to cast this spell, pay X life.
All creatures get -X/-X until end of turn.

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.

Flare of Denial

You may sacrifice a nontoken blue creature rather than pay this spell's mana cost.
Counter target spell.

Boromir, Warden of the Tower

Vigilance
Whenever an opponent casts a spell, if no mana was spent to cast it, counter that spell.
Sacrifice Boromir, Warden of the Tower: Creatures you control gain indestructible until end of turn. The Ring tempts you.

Vault of Champions

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

Heroic Intervention

Permanents you control gain hexproof and indestructible until end of turn.

Consecrated Sphinx

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

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.

Abrupt Decay

This spell can't be countered.
Destroy target nonland permanent with mana value 3 or less.

Shipwreck Marsh

Shipwreck Marsh enters tapped unless you control two or more other lands.
{T}: Add {U} or {B}.

Snap

Return target creature to its owner's hand. Untap up to two lands.