Opposition Agent

Flash
You control your opponents while they're searching their libraries.
While an opponent is searching their library, they exile each card they find. You may play those cards for as long as they remain exiled, and you may spend mana as though it were mana of any color to cast them.

Verdant Catacombs

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

Thassa's Oracle

When this creature enters, look at the top X cards of your library, where X is your devotion to blue. Put up to one of them on top of your library and the rest on the bottom of your library in a random order. If X is greater than or equal to the number of cards in your library, you win the game. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Orcish Bowmasters

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

Touch the Spirit Realm

When this enchantment enters, exile up to one target artifact or creature until this enchantment leaves the battlefield.
Channel — {1}{W}, Discard this card: Exile target artifact or creature. Return it to the battlefield under its owner's control at the beginning of the next end step.

Polluted Delta

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

Talisman of Dominance

{T}: Add {C}.
{T}: Add {U} or {B}. This artifact deals 1 damage to you.

Force of Negation

If it's not your turn, you may exile a blue card from your hand rather than pay this spell's mana cost.
Counter target noncreature spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

City of Brass

Whenever this land becomes tapped, it deals 1 damage to you.
{T}: Add one mana of any color.

Displacer Kitten

Avoidance — Whenever you cast a noncreature spell, exile up to one target nonland permanent you control, then return that card to the battlefield under its owner's control.

Sevinne's Reclamation

Return target permanent card with mana value 3 or less from your graveyard to the battlefield. If this spell was cast from a graveyard, you may copy this spell and may choose a new target for the copy.
Flashback {4}{W} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Flooded Strand

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

Demonic Consultation

Choose a card name. Exile the top six cards of your library, then reveal cards from the top of your library until you reveal a card with the chosen name. Put that card into your hand and exile all other cards revealed this way.

Imperial Seal

Search your library for a card, then shuffle and put that card on top. You lose 2 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.

Arid Mesa

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

Delay

Counter target spell. If the spell is countered this way, exile it with three time counters on it instead of putting it into its owner's graveyard. If it doesn't have suspend, it gains suspend. (At the beginning of its owner's upkeep, they remove a time counter. When the last is removed, they may play it without paying its mana cost. If it's a creature, it has haste.)

Teferi, Time Raveler

Each opponent can cast spells only any time they could cast a sorcery.
+1: Until your next turn, you may cast sorcery spells as though they had flash.
−3: Return up to one target artifact, creature, or enchantment to its owner's hand. Draw a card.

Esper Sentinel

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

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 token: Add one mana of any color.")

Misty Rainforest

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

Flusterstorm

Counter target instant or sorcery spell unless its controller pays {1}.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Drannith Magistrate

Your opponents can't cast spells from anywhere other than their hands.

Mana Drain

Counter target spell. At the beginning of your next main phase, add an amount of {C} equal to that spell's mana value.

Windswept Heath

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

Enlightened Tutor

Search your library for an artifact or enchantment card, reveal it, then shuffle and put that card on top.

Silence

Your opponents can't cast spells this turn.

Mana Vault

This artifact doesn't untap during your untap step.
At the beginning of your upkeep, you may pay {4}. If you do, untap this artifact.
At the beginning of your draw step, if this artifact is tapped, it deals 1 damage to you.
{T}: Add {C}{C}{C}.

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.")

Toxic Deluge

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

Phantasmal Image

You may have this creature enter as a copy of any creature on the battlefield, except it's an Illusion in addition to its other types and it has "When this creature becomes the target of a spell or ability, sacrifice it."

Vampiric Tutor

Mental Misstep

({U/P} can be paid with either {U} or 2 life.)
Counter target spell with mana value 1.

The One Ring

Indestructible
When The One Ring enters, if you cast it, you gain protection from everything until your next turn.
At the beginning of your upkeep, you lose 1 life for each burden counter on The One Ring.
{T}: Put a burden counter on The One Ring, then draw a card for each burden counter on The One Ring.

Force of Will

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.
Counter target spell.

Pact of Negation

Counter target spell.
At the beginning of your next upkeep, pay {3}{U}{U}. If you don't, you lose the game.

Chrome Mox

Imprint — When this artifact enters, you may exile a nonartifact, nonland card from your hand.
{T}: Add one mana of any of the exiled card's colors.

Grim Monolith

This artifact doesn't untap during your untap step.
{T}: Add {C}{C}{C}.
{4}: Untap this artifact.