Spell Pierce

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

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Hallowed Fountain

({T}: Add {W} or {U}.)
As Hallowed Fountain enters, you may pay 2 life. If you don't, it enters tapped.

Temple Garden

({T}: Add {G} or {W}.)
As Temple Garden enters, you may pay 2 life. If you don't, it enters tapped.

Memory Lapse

Counter target spell. If that spell is countered this way, put it on top of its owner's library instead of into that player's graveyard.

Fateful Absence

Destroy target creature or planeswalker. Its controller investigates. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Teferi, Time Raveler

Each opponent can cast spells only any time they could cast a sorcery.
+1: Until your next turn, you may cast sorcery spells as though they had flash.
−3: Return up to one target artifact, creature, or enchantment to its owner's hand. Draw a card.

Breeding Pool

({T}: Add {G} or {U}.)
As Breeding Pool enters, you may pay 2 life. If you don't, it enters tapped.

The Wandering Emperor

Flash
As long as The Wandering Emperor entered this turn, you may activate her loyalty abilities any time you could cast an instant.
+1: Put a +1/+1 counter on up to one target creature. It gains first strike until end of turn.
−1: Create a 2/2 white Samurai creature token with vigilance.
−2: Exile target tapped creature. You gain 2 life.

Seachrome Coast

Seachrome Coast enters tapped unless you control two or fewer other lands.
{T}: Add {W} or {U}.

Teferi, Hero of Dominaria

+1: Draw a card. At the beginning of the next end step, untap up to two lands.
−3: Put target nonland permanent into its owner's library third from the top.
−8: You get an emblem with "Whenever you draw a card, exile target permanent an opponent controls."

Spara's Headquarters

({T}: Add {G}, {W}, or {U}.)
Spara's Headquarters enters tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

Counterspell

Oko, Thief of Crowns

+2: Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
+1: Target artifact or creature loses all abilities and becomes a green Elk creature with base power and toughness 3/3.
−5: Exchange control of target artifact or creature you control and target creature an opponent controls with power 3 or less.