Mundungu

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

Disruptive Student

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

Etherium-Horn Sorcerer

{1}{U}{R}: Return Etherium-Horn Sorcerer to its owner's hand.
Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Sunken Field

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

Vodalian Mage

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

Disrupt

Counter target instant or sorcery spell unless its controller pays {1}.
Draw a card.

Unwind

Counter target noncreature spell. Untap up to three lands.

Mirran Spy

Flying
Whenever you cast an artifact spell, you may untap target creature.

Neera, Wild Mage

Whenever you cast a spell, you may put it on the bottom of its owner's library. If you do, reveal cards from the top of your library until you reveal a nonland card. You may cast that card without paying its mana cost. Then put all revealed cards not cast this way on the bottom of your library in a random order. This ability triggers only once each turn.

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.)

Dream Fracture

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

Rewind

Counter target spell. Untap up to four lands.

Forceful Denial

Cascade (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)
Counter target spell.

Counterlash

Counter target spell. You may cast a spell that shares a card type with it from your hand without paying its mana cost.

Mishra, Artificer Prodigy

Whenever you cast an artifact spell, you may search your graveyard, hand, and/or library for a card with the same name as that spell and put it onto the battlefield. If you search your library this way, shuffle.

Fold into Aether

Counter target spell. If that spell is countered this way, its controller may put a creature card from their hand onto the battlefield.