Counterspell

Sol Ring

Seedborn Muse

Untap all permanents you control during each other player's untap step.

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.

Eternal Witness

When Eternal Witness enters, you may return target card from your graveyard to your hand.

Beast Within

Destroy target permanent. Its controller creates a 3/3 green Beast creature token.

Rashmi, Eternities Crafter

Whenever you cast your first spell each turn, reveal the top card of your library. You may cast it without paying its mana cost if it's a spell with lesser mana value. If you don't cast it, put it into your hand.

Mystic Snake

Flash
When Mystic Snake enters, counter target spell.

Frilled Mystic

Flash
When Frilled Mystic enters, you may counter target spell.

Thought Sponge

Flash
Thought Sponge enters with a number of +1/+1 counters on it equal to the greatest number of cards an opponent has drawn this turn.
When Thought Sponge dies, draw cards equal to its power.

Wilderness Reclamation

At the beginning of your end step, untap all lands you control.

Venser, Shaper Savant

Flash (You may cast this spell any time you could cast an instant.)
When Venser, Shaper Savant enters, return target spell or permanent to its owner's hand.