Underworld Dreams

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

River Kelpie

Whenever River Kelpie or another permanent enters from a graveyard, draw a card.
Whenever a player casts a spell from a graveyard, draw a card.
Persist (When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.)

Island

Painful Quandary

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

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Niv-Mizzet, Parun

This spell can't be countered.
Flying
Whenever you draw a card, Niv-Mizzet, Parun deals 1 damage to any target.
Whenever a player casts an instant or sorcery spell, you draw a card.

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.

Snake Pit

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

Forest

Arcane Signet

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

Zagoth Triome

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

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.

Gruul Signet

Dragon's Claw

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

Mindcrank

Whenever an opponent loses life, that player mills that many cards. (Damage causes loss of life.)

Compost

Whenever a black card is put into an opponent's graveyard from anywhere, you may draw a card.

Mystic Monastery

Mystic Monastery enters tapped.
{T}: Add {U}, {R}, or {W}.

Orzhov Signet

Kraken's Eye

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

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.

Kavu Predator

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

Mazirek, Kraul Death Priest

Flying
Whenever a player sacrifices another permanent, put a +1/+1 counter on each creature you control.

Ketria Triome

({T}: Add {G}, {U}, or {R}.)
Ketria Triome enters tapped.
Cycling {3} ({3}, Discard this card: 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.

Mold Adder

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

Havoc

Whenever an opponent casts a white spell, they lose 2 life.

Nath of the Gilt-Leaf

At the beginning of your upkeep, you may have target opponent discard a card at random.
Whenever an opponent discards a card, you may create a 1/1 green Elf Warrior creature token.

Managorger Hydra

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

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.

Demon's Horn

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

Rakdos Signet

Dimir Signet

Opulent Palace

Opulent Palace enters tapped.
{T}: Add {B}, {G}, or {U}.

Azorius Signet

Golos, Tireless Pilgrim

When Golos, Tireless Pilgrim enters, you may search your library for a land card, put that card onto the battlefield tapped, then shuffle.
{2}{W}{U}{B}{R}{G}: Exile the top three cards of your library. You may play them this turn without paying their mana costs.

Warmth

Whenever an opponent casts a red spell, you gain 2 life.

Boros Signet

Liliana's Caress

Whenever an opponent discards a card, that player loses 2 life.

Algae Gharial

Shroud (This creature can't be the target of spells or abilities.)
Whenever another creature dies, you may put a +1/+1 counter on Algae Gharial.

Mind's Eye

Whenever an opponent draws a card, you may pay {1}. If you do, draw a card.

Dirtcowl Wurm

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

Memory Erosion

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

Wurm's Tooth

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

Kaervek the Merciless

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

Kambal, Consul of Allocation

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

Ruric Thar, the Unbowed

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

Bloodstained Mire

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

Sandsteppe Citadel

Sandsteppe Citadel enters tapped.
{T}: Add {W}, {B}, or {G}.

Fate Unraveler

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

Thraximundar

Haste
Whenever Thraximundar attacks, defending player sacrifices a creature.
Whenever a player sacrifices a creature, you may put a +1/+1 counter on Thraximundar.

Crumbling Necropolis

Crumbling Necropolis enters tapped.
{T}: Add {U}, {B}, or {R}.

Selesnya Signet

Simic Signet

Savai Triome

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

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.

Pain Magnification

Whenever an opponent is dealt 3 or more damage by a single source, that player discards 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.

Soldier of the Pantheon

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

Cosi's Trickster

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

Runic Armasaur

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

Ob Nixilis, the Hate-Twisted

Whenever an opponent draws a card, Ob Nixilis, the Hate-Twisted deals 1 damage to that player.
−2: Destroy target creature. Its controller draws two cards.

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.

Swamp

Nekusar, the Mindrazer

At the beginning of each player's draw step, that player draws an additional card.
Whenever an opponent draws a card, Nekusar, the Mindrazer deals 1 damage to that player.

Soul Barrier

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

Mayhem Devil

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

Paradise Plume

As Paradise Plume enters, 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.

Reparations

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

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.

Sanctimony

Whenever an opponent taps a Mountain for mana, you may gain 1 life.

Frontier Bivouac

Frontier Bivouac enters tapped.
{T}: Add {G}, {U}, or {R}.

Jungle Shrine

Jungle Shrine enters tapped.
{T}: Add {R}, {G}, or {W}.

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.

Waste Not

Whenever an opponent discards a creature card, create a 2/2 black Zombie creature token.
Whenever an opponent discards a land card, add {B}{B}.
Whenever an opponent discards a noncreature, nonland card, draw a card.

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.

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.

Harsh Mentor

Whenever an opponent activates an ability of an artifact, creature, or land on the battlefield, if it isn't a mana ability, Harsh Mentor deals 2 damage to that player.

Command Tower

Heartwood Storyteller

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

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.

Spelltithe Enforcer

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

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.

Sangromancer

Flying
Whenever a creature an opponent controls dies, you may gain 3 life.
Whenever an opponent discards a card, you may gain 3 life.

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.

Sunscorch Regent

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

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.)

Dragonlair Spider

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

Immolation Shaman

Whenever an opponent activates an ability of an artifact, creature, or land that isn't a mana ability, Immolation Shaman deals 1 damage to that player.
{3}{R}{R}: Immolation Shaman gets +3/+3 and gains menace until end of turn.

Raugrin Triome

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

Kor Firewalker

Protection from red
Whenever a player casts a red spell, you may gain 1 life.

Ob Nixilis, Unshackled

Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis, Unshackled.

Golgari Signet

Burgeoning

Whenever an opponent plays a land, you may put a land card from your hand onto the battlefield.

Citanul Druid

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

Arcane Sanctum

Arcane Sanctum enters tapped.
{T}: Add {W}, {U}, or {B}.

Rewards of Diversity

Whenever an opponent casts a multicolored spell, you gain 4 life.

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.

Wooded Foothills

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

Consecrated Sphinx

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

Exquisite Blood

Whenever an opponent loses life, you gain that much life.

Oppression

Whenever a player casts a spell, that player discards a card.

Ichneumon Druid

Whenever an opponent casts an instant spell other than the first instant spell that player casts each turn, Ichneumon Druid deals 4 damage to that player.

Nomad Outpost

Nomad Outpost enters tapped.
{T}: Add {R}, {W}, or {B}.

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.

Noosegraf Mob

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

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Insight

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