Lose Focus

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

Ertai's Scorn

This spell costs {U} less to cast if an opponent cast two or more spells this turn.
Counter target spell.

Negate

Dream Fracture

Counter target spell. Its controller draws a card.
Draw a card.

Bane's Contingency

Counter target spell. If that spell targets a commander you control, instead counter that spell, scry 2, then draw a card.

Thought Collapse

Counter target spell. Its controller mills three cards.

Essence Scatter

Psychic Rebuttal

Counter target instant or sorcery spell that targets you.
Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, you may copy the spell countered this way. You may choose new targets for the copy.

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.

Revolutionary Rebuff

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

Tolarian Terror

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)

Out of Air

This spell costs {2} less to cast if it targets a creature spell.
Counter target spell.