This spell costs less to cast during your turn.
Tap target artifact or creature.
Draw a card.

Mill two cards.
Draw a card.

Counter target spell with mana value 3 or less. (Then exile this card. You may cast the creature later from exile.)

Improvise
Counter target spell unless its controller pays .

Spree (Choose one or more additional costs.)
+ — Until end of turn, target creature becomes a white Rabbit with base power and toughness 0/1.
+ — Target player draws two cards.

Put target permanent an opponent controls on top of its owner's library. That opponent may put an artifact, creature, enchantment, or land card from their hand onto the battlefield.

Counter target spell. That spell's controller reveals their hand, then discards each card with the same name as a card spliced onto that spell.

Change the text of target permanent by replacing all instances of one color word with another or one basic land type with another. (For example, you may change "nonblack creature" to "nongreen creature" or "forestwalk" to "plainswalk." This effect lasts indefinitely.)

Buyback
Tap target artifact, creature, or land.

Until end of turn, target artifact or creature becomes an artifact creature with base power and toughness 4/5.
Draw a card.

If an opponent cast three or more spells this turn, you may pay rather than pay this spell's mana cost.
Exile any number of target spells.

Counter target spell unless its controller pays .

Counter target spell with mana value 1 or less.

Cast this spell only during the declare blockers step.
For each creature attacking you or a planeswalker you control, create a token that's a copy of that creature and that's blocking that creature. Exile those tokens at end of combat.

Each nonland permanent you control becomes a copy of target non-Aura permanent.

Counter target spell unless its controller pays .
Cycling

Counter target instant or sorcery spell unless its controller pays .

You may exile a blue card from your hand rather than pay this spell's mana cost.
Change the target of target spell with a single target.

Name a nonland card, then reveal the top card of your library. If that card is the named card, draw three cards.

Target creature's owner puts it on their choice of the top or bottom of their library.

Surveil 2, then choose an instant or sorcery card in your graveyard. You may cast it this turn. If that spell would be put into your graveyard, exile it instead.

Target creature you control gets +0/+1 and gains hexproof until end of turn.
Overload

Each player shuffles their graveyard into their library.

Look at the top three cards of your library. Put one of those cards into your hand, one into your graveyard, and one on the bottom of your library.

Target spell or permanent becomes colorless.

Until end of turn, target creature becomes a Dragon with base power and toughness 4/4 and gains flying. (It loses all other creature types.)

Add or subtract 1 or one from a number or number word on target spell or permanent until end of turn.

Counter target instant or sorcery spell.
Transmute

Reveal the top three cards of your library. An opponent chooses one of them. Put that card into your graveyard and the rest into your hand.

Create a 3/3 blue and red Elemental creature token with flying.
Surveil 2.