Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Annul

Counter target artifact or enchantment spell.

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.)

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.

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.

Circular Logic

Counter target spell unless its controller pays {1} for each card in your graveyard.
Madness {U} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Aether Syphon

Start your engines! (If you have no speed, it starts at 1. It increases once on each of your turns when an opponent loses life. Max speed is 4.)
{2}, {T}: Draw a card.
Max speed — Whenever you draw a card, each opponent mills two cards. (Each opponent puts the top two cards of their library into their graveyard.)

Refute

Counter target spell. Draw a card, then discard a card.

Counterspell

Access Denied

Counter target spell. Create X 1/1 colorless Thopter artifact creature tokens with flying, where X is that spell's mana value.

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 this card: Counter target spell or ability unless its controller pays {3}.

Lilting Refrain

At the beginning of your upkeep, you may put a verse counter on this enchantment.
Sacrifice this enchantment: Counter target spell unless its controller pays {X}, where X is the number of verse counters on this enchantment.

Bone to Ash

Counter target creature spell.
Draw a card.

Negate

Aetherize

Return all attacking creatures to their owner's hand.

An Offer You Can't Refuse

Counter target noncreature spell. Its controller creates two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

Propaganda

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

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Alandra, Sky Dreamer

Whenever you draw your second card each turn, create a 2/2 blue Drake creature token with flying.
Whenever you draw your fifth card each turn, Alandra and Drakes you control each get +X/+X until end of turn, where X is the number of cards in your hand.

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.

Ominous Seas

Whenever you draw a card, put a foreshadow counter on this enchantment.
Remove eight foreshadow counters from this enchantment: Create an 8/8 blue Kraken creature token.
Cycling {2} ({2}, Discard this card: Draw a card.)

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.

Amazing Acrobatics

Choose one or both —
• Counter target spell.
• Tap one or two target creatures.