Soratami Savant

Flying
{3}, Return a land you control to its owner's hand: Counter target spell unless its controller pays {3}.

Daring Apprentice

{T}, Sacrifice Daring Apprentice: Counter target spell.

Wizard Replica

Flying
{U}, Sacrifice Wizard Replica: Counter target spell unless its controller pays {2}.

Benevolent Geist

Flying
Noncreature spells you control can't be countered.
If Benevolent Geist would be put into a graveyard from anywhere, exile it instead.

Malevolent Hermit

{U}, Sacrifice Malevolent Hermit: Counter target noncreature spell unless its controller pays {3}.
Disturb {2}{U} (You may cast this card from your graveyard transformed for its disturb cost.)

Malevolent Hermit // Benevolent Geist

Spiketail Drake

Flying
Sacrifice Spiketail Drake: Counter target spell unless its controller pays {3}.

Voidmage Prodigy

{U}{U}, Sacrifice a Wizard: Counter target spell.
Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Siren Stormtamer

Flying
{U}, Sacrifice Siren Stormtamer: Counter target spell or ability that targets you or a creature you control.

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Venser, Shaper Savant

Flash
When Venser, Shaper Savant enters the battlefield, return target spell or permanent to its owner's hand.

Brine Seer

{2}{U}, {T}: Reveal any number of blue cards in your hand. Counter target spell unless its controller pays {1} for each card revealed this way.

Arcane Signet

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

Mists of Lórien

Replicate {U} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Return target nonland permanent and each other nonland permanent with the same mana value as that permanent to their owners' hands.

Ghost-Lit Warder

{3}{U}, {T}: Counter target spell unless its controller pays {2}.
Channel — {3}{U}, Discard Ghost-Lit Warder: Counter target spell unless its controller pays {4}.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Nimble Obstructionist

Flash
Flying
Cycling {2}{U} ({2}{U}, Discard this card: Draw a card.)
When you cycle Nimble Obstructionist, counter target activated or triggered ability you don't control.

Otawara, Soaring City

{T}: Add {U}.
Channel — {3}{U}, Discard Otawara, Soaring City: Return target artifact, creature, enchantment, or planeswalker to its owner's hand. This ability costs {1} less to activate for each legendary creature you control.

Jin-Gitaxias, Progress Tyrant

Whenever you cast an artifact, instant, or sorcery spell, copy that spell. You may choose new targets for the copy. This ability triggers only once each turn. (A copy of a permanent spell becomes a token.)
Whenever an opponent casts an artifact, instant, or sorcery spell, counter that spell. This ability triggers only once each turn.

Draining Whelk

Flash
Flying
When Draining Whelk enters the battlefield, counter target spell. Put X +1/+1 counters on Draining Whelk, where X is that spell's mana value.

Tishana's Tidebinder

Flash
When Tishana's Tidebinder enters the battlefield, counter up to one target activated or triggered ability. If an ability of an artifact, creature, or planeswalker is countered this way, that permanent loses all abilities for as long as Tishana's Tidebinder remains on the battlefield. (Mana abilities can't be targeted.)

Lonely Sandbar

Lonely Sandbar enters the battlefield tapped.
{T}: Add {U}.
Cycling {U} ({U}, Discard this card: Draw a card.)

Baral, Chief of Compliance

Instant and sorcery spells you cast cost {1} less to cast.
Whenever a spell or ability you control counters a spell, you may draw a card. If you do, discard a card.

Cursecatcher

Sacrifice Cursecatcher: Counter target instant or sorcery spell unless its controller pays {1}.

Stonybrook Banneret

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Merfolk spells and Wizard spells you cast cost {1} less to cast.

Disruptive Student

{T}: Counter target spell unless its controller pays {1}.

Azami, Lady of Scrolls

Tap an untapped Wizard you control: Draw a card.

Stronghold Machinist

{U}{U}, {T}, Discard a card: Counter target noncreature spell.

Riptide Laboratory

{T}: Add {C}.
{1}{U}, {T}: Return target Wizard you control to its owner's hand.

Snow-Covered Island

Throne of Eldraine

As Throne of Eldraine enters the battlefield, choose a color.
{T}: Add four mana of the chosen color. Spend this mana only to cast monocolored spells of that color.
{3}, {T}: Draw two cards. Spend only mana of the chosen color to activate this ability.

Eaten by Piranhas

Flash
Enchant creature
Enchanted creature loses all abilities and is a black Skeleton creature with base power and toughness 1/1. (It loses all other card types and creature types.)

Adric, Mathematical Genius

{2}{U}, {T}: Copy target activated or triggered ability you control. You may choose new targets for the copy.
Ultimate Sacrifice — {1}{U}, Sacrifice Adric: Counter target activated or triggered ability.
Doctor's companion (You can have two commanders if the other is the Doctor.)

Glen Elendra Archmage

Flying
{U}, Sacrifice Glen Elendra Archmage: Counter target noncreature spell.
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.)

Faerie Mastermind

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

Patron Wizard

Tap an untapped Wizard you control: Counter target spell unless its controller pays {1}.

Spiketail Drakeling

Flying
Sacrifice Spiketail Drakeling: Counter target spell unless its controller pays {2}.

Wizard Class

(Gain the next level as a sorcery to add its ability.)
You have no maximum hand size.
{2}{U}: Level 2
When this Class becomes level 2, draw two cards.
{4}{U}: Level 3
Whenever you draw a card, put a +1/+1 counter on target creature you control.

Lullmage Mentor

Whenever a spell or ability you control counters a spell, you may create a 1/1 blue Merfolk creature token.
Tap seven untapped Merfolk you control: Counter target spell.

Silumgar Spell-Eater

Megamorph {4}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)
When Silumgar Spell-Eater is turned face up, counter target spell unless its controller pays {3}.

Sigil Tracer

{1}{U}, Tap two untapped Wizards you control: Copy target instant or sorcery spell. You may choose new targets for the copy.

Martyr of Frost

{2}, Reveal X blue cards from your hand, Sacrifice Martyr of Frost: Counter target spell unless its controller pays {X}.

Midnight Clock

{T}: Add {U}.
{2}{U}: Put an hour counter on Midnight Clock.
At the beginning of each upkeep, put an hour counter on Midnight Clock.
When the twelfth hour counter is put on Midnight Clock, shuffle your hand and graveyard into your library, then draw seven cards. Exile Midnight Clock.

Disruptive Pitmage

{T}: Counter target spell unless its controller pays {1}.
Morph {U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Cerulean Drake

Flying
Protection from red (This creature can't be blocked, targeted, dealt damage, enchanted, or equipped by anything red.)
Sacrifice Cerulean Drake: Counter target spell that targets you.

Decree of Silence

Whenever an opponent casts a spell, counter that spell and put a depletion counter on Decree of Silence. If there are three or more depletion counters on Decree of Silence, sacrifice it.
Cycling {4}{U}{U} ({4}{U}{U}, Discard this card: Draw a card.)
When you cycle Decree of Silence, you may counter target spell.

Sol Talisman

Suspend 3—{1} (Rather than cast this card from your hand, pay {1} and exile it with three 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.)
{T}: Add {C}{C}.

Leyline of Anticipation

If Leyline of Anticipation is in your opening hand, you may begin the game with it on the battlefield.
You may cast spells as though they had flash.

Hydromorph Guardian

{U}, Sacrifice Hydromorph Guardian: Counter target spell that targets a creature you control.

Rhystic Study

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

Misleading Signpost

Flash
When Misleading Signpost enters the battlefield during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)
{T}: Add {U}.

Sunken Field

Enchant land
Enchanted land has "{T}: Counter target spell unless its controller pays {1}."

Sky Diamond

Sky Diamond enters the battlefield tapped.
{T}: Add {U}.

Vodalian Mage

{U}, {T}: Counter target spell unless its controller pays {1}.

Arcanis the Omnipotent

{T}: Draw three cards.
{2}{U}{U}: Return Arcanis the Omnipotent to its owner's hand.

Spiketail Hatchling

Flying (This creature can't be blocked except by creatures with flying or reach.)
Sacrifice Spiketail Hatchling: Counter target spell unless its controller pays {1}.

Telepathy

Your opponents play with their hands revealed.

Myriad Landscape

Myriad Landscape enters the battlefield tapped.
{T}: Add {C}.
{2}, {T}, Sacrifice Myriad Landscape: Search your library for up to two basic land cards that share a land type, put them onto the battlefield tapped, then shuffle.

Teferi, Mage of Zhalfir

Flash
Creature cards you own that aren't on the battlefield have flash.
Each opponent can cast spells only any time they could cast a sorcery.

Treasure Cruise

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Draw three cards.

Guile

Guile can't be blocked except by three or more creatures.
If a spell or ability you control would counter a spell, instead exile that spell and you may play that card without paying its mana cost.
When Guile is put into a graveyard from anywhere, shuffle it into its owner's library.

Diplomatic Escort

{U}, {T}, Discard a card: Counter target spell or ability that targets a creature.

Archmage of Echoes

Flying, ward {2}
Whenever you cast a Faerie or Wizard permanent spell, copy it. (The copy becomes a token.)

Rimewind Cryomancer

{1}, {T}: Counter target activated ability. Activate only if you control four or more snow permanents. (Mana abilities can't be targeted.)

Voidmage Apprentice

Morph {2}{U}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Voidmage Apprentice is turned face up, counter target spell.

Vodalian Hexcatcher

Flash
Other Merfolk you control get +1/+1.
Sacrifice a Merfolk: Counter target noncreature spell unless its controller pays {1}.

Thought Vessel

Hydromorph Gull

Flying
{U}, Sacrifice Hydromorph Gull: Counter target spell that targets a creature you control.

Psychic Trance

Until end of turn, Wizards you control gain "{T}: Counter target spell."

Kira, Great Glass-Spinner

Flying
Creatures you control have "Whenever this creature becomes the target of a spell or ability for the first time each turn, counter that spell or ability."

Stronghold Biologist

{U}{U}, {T}, Discard a card: Counter target creature spell.

Ertai, Wizard Adept

Windfall

Each player discards their hand, then draws cards equal to the greatest number of cards a player discarded this way.

Mirrorshell Crab

Ward {3} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
Channel — {2}{U}, Discard Mirrorshell Crab: Counter target spell or ability unless its controller pays {3}.

Kheru Spellsnatcher

Morph {4}{U}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Kheru Spellsnatcher is turned face up, counter target spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard. You may cast that card without paying its mana cost for as long as it remains exiled.

Stratus Dancer

Flying
Megamorph {1}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)
When Stratus Dancer is turned face up, counter target instant or sorcery spell.