Nils, Discipline Enforcer

At the beginning of your end step, for each player, put a +1/+1 counter on up to one target creature that player controls.
Each creature with one or more counters on it can't attack you or planeswalkers you control unless its controller pays {X}, where X is the number of counters on that creature.

Sunscorch Regent

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

Valkmira, Protector's Shield

If a source an opponent controls would deal damage to you or a permanent you control, prevent 1 of that damage.
Whenever you or another permanent you control becomes the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays {1}.

Reidane, God of the Worthy

Flying, vigilance
Snow lands your opponents control enter tapped.
Noncreature spells your opponents cast with mana value 4 or greater cost {2} more to cast.

Reidane, God of the Worthy // Valkmira, Protector's Shield

Spelltithe Enforcer

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

Lightshield Array

At the beginning of your end step, put a +1/+1 counter on each creature that attacked this turn.
Sacrifice Lightshield Array: Creatures you control gain hexproof and indestructible until end of turn.

Invasion of Gobakhan

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When Invasion of Gobakhan enters, look at target opponent's hand. You may exile a nonland card from it. For as long as that card remains exiled, its owner may play it. A spell cast this way costs {2} more to cast.

Invasion of Gobakhan // Lightshield Array

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.

Arcane Signet

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

Sheoldred, the Apocalypse

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

Kambal, Profiteering Mayor

Whenever one or more tokens your opponents control enter, for each of them, create a tapped token that's a copy of it. This ability triggers only once each turn.
Whenever one or more tokens you control enter, each opponent loses 1 life and you gain 1 life.

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.")

Bennie Bracks, Zoologist

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
At the beginning of each end step, if you created a token this turn, draw a card.

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.

Underworld Dreams

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

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.

Strict Proctor

Flying
Whenever a permanent entering causes a triggered ability to trigger, counter that ability unless its controller pays {2}.

Mastermind Plum

Whenever Mastermind Plum attacks, exile up to one target card from a graveyard. If an artifact card was exiled this way, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Whenever you cast a spell, if mana from a Treasure was spent to cast it, you draw a card and you lose 1 life.

Indulgent Tormentor

Flying
At the beginning of your upkeep, draw a card unless target opponent sacrifices a creature of their choice or pays 3 life.

Braids, Arisen Nightmare

At the beginning of your end step, you may sacrifice an artifact, creature, enchantment, land, or planeswalker. If you do, each opponent may sacrifice a permanent of their choice that shares a card type with it. For each opponent who doesn't, that player loses 2 life and you draw a card.

Sol Ring

Smuggler's Share

At the beginning of each end step, draw a card for each opponent who drew two or more cards this turn, then create a Treasure token for each opponent who had two or more lands enter the battlefield under their control this turn.

Inkshield

Prevent all combat damage that would be dealt to you this turn. For each 1 damage prevented this way, create a 2/1 white and black Inkling creature token with flying.

Ghostly Prison

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

Amulet of Safekeeping

Whenever you become the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays {1}.
Creature tokens get -1/-0.

Wrath of God

Destroy all creatures. They can't be regenerated.

Darksteel Mutation

Enchant creature
Enchanted creature is an Insect artifact creature with base power and toughness 0/1 and has indestructible, and it loses all other abilities, card types, and creature types.

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.

Damnation

Mage Hunter

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

Soul Partition

Exile target nonland permanent. For as long as that card remains exiled, its owner may play it. A spell cast by an opponent this way costs {2} more to cast.

Archivist of Oghma

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

Nadier's Nightblade

Whenever a token you control leaves the battlefield, each opponent loses 1 life and you gain 1 life.

Mind's Eye

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

Fellwar Stone

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

Tithe Taker

During your turn, spells your opponents cast cost {1} more to cast and abilities your opponents activate cost {1} more to activate unless they're mana abilities.
Afterlife 1 (When this creature dies, create a 1/1 white and black Spirit creature token with flying.)

Tomik, Wielder of Law

Affinity for planeswalkers (This spell costs {1} less to cast for each planeswalker you control.)
Flying, vigilance
Whenever an opponent attacks with creatures, if two or more of those creatures are attacking you and/or planeswalkers you control, that opponent loses 3 life and you draw a card.

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.

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.

Mana Tithe

Counter target spell unless its controller pays {1}.

Sword-Point Diplomacy

Reveal the top three cards of your library. For each of those cards, put that card into your hand unless any opponent pays 3 life. Then exile the rest.

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.

Painful Quandary

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

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.")

Orzhov Signet

Windborn Muse

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

Cowed by Wisdom

Enchant creature
Enchanted creature can't attack or block unless its controller pays {1} for each card in your hand.

Fate Unraveler

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

Elite Spellbinder

Flying
When Elite Spellbinder enters, look at target opponent's hand. You may exile a nonland card from it. For as long as that card remains exiled, its owner may play it. A spell cast this way costs {2} more to cast.

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.

Isolation Cell

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

Brainwash

Enchant creature
Enchanted creature can't attack unless its controller pays {3}.

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

Talisman of Hierarchy

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

Kambal, Consul of Allocation

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

Oppressive Rays

Enchant creature
Enchanted creature can't attack or block unless its controller pays {3}.
Activated abilities of enchanted creature cost {3} more to activate.

Monologue Tax

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