Fate Unraveler

Whenever an opponent draws a card, Fate Unraveler deals 1 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.

Memory Erosion

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

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.

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.)

Knights of the Black Rose

When Knights of the Black Rose enters, you become the monarch.
Whenever an opponent becomes the monarch, if you were the monarch as the turn began, that player loses 2 life and you gain 2 life.

Ob Nixilis, Unshackled

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

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}.

Isperia, Supreme Judge

Flying
Whenever a creature attacks you or a planeswalker you control, you may draw 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.

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.

Underworld Dreams

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

Ever-Watching Threshold

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

Hissing Miasma

Whenever a creature attacks you, its controller loses 1 life.

Faerie Mastermind

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

Baird, Steward of Argive

Vigilance
Creatures can't attack you or planeswalkers you control unless their controller pays {1} for each of those creatures.

Isolation Cell

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

Consecrated Sphinx

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

Revenge of Ravens

Whenever a creature attacks you or a planeswalker you control, that creature's controller loses 1 life and you gain 1 life.

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.

Lightmine Field

Whenever one or more creatures attack, Lightmine Field deals damage to each of those creatures equal to the number of attacking creatures.

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.

Ankh of Mishra

Whenever a land enters, Ankh of Mishra deals 2 damage to that land's controller.

Exquisite Blood

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

Ghostly Prison

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Sheoldred, the Apocalypse

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

Mind's Eye

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

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.

Kambal, Consul of Allocation

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

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.

Archon of Absolution

Flying
Protection from white (This creature can't be blocked, targeted, dealt damage, enchanted, or equipped by anything white.)
Creatures can't attack you or planeswalkers you control unless their controller pays {1} for each of those creatures.

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.

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.

Orcish Bowmasters

Flash
When Orcish Bowmasters enters 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.

Fact or Fiction

Reveal the top five cards of your library. An opponent separates those cards into two piles. Put one pile into your hand and the other into your graveyard.

Reparations

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

Windborn Muse

Flying
Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Orzhov Advokist

At the beginning of your upkeep, each player may put two +1/+1 counters on a creature they control. If a player does, creatures that player controls can't attack you or planeswalkers you control until your next turn.

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.

Wedding Ring

When Wedding Ring enters, 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.

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.

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.)

Propaganda

Norn's Decree

Whenever one or more creatures an opponent controls deal combat damage to you, that opponent gets a poison counter.
Whenever a player attacks, if one or more players being attacked are poisoned, the attacking player draws a card.

Cunning Rhetoric

Whenever an opponent attacks you and/or one or more planeswalkers you control, exile the top card of that player's library. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast it.

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.")

Painful Quandary

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

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

Monologue Tax

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

Sunscorch Regent

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

Michiko Konda, Truth Seeker

Whenever a source an opponent controls deals damage to you, that player sacrifices a permanent of your choice.

Norn's Annex

({W/P} can be paid with either {W} or 2 life.)
Creatures can't attack you or planeswalkers you control unless their controller pays {W/P} for each of those creatures.

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.

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.

Rhystic Study

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