Ertai Resurrected

Flash
When Ertai Resurrected enters, choose up to one —
• Counter target spell, activated ability, or triggered ability. Its controller draws a card.
• Destroy another target creature or planeswalker. Its controller draws a card.

Portal Mage

Flash
When Portal Mage enters during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)

Hullbreaker Horror

Flash
This spell can't be countered.
Whenever you cast a spell, choose up to one —
• Return target spell you don't control to its owner's hand.
• Return target nonland permanent to its owner's hand.

Slitherwisp

Flash
Whenever you cast another spell that has flash, you draw a card and each opponent loses 1 life.

Glademuse

Whenever a player casts a spell, if it's not their turn, that player draws a card.

Alexi's Cloak

Flash
Enchant creature
Enchanted creature has shroud. (It can't be the target of spells or abilities.)

Growth Spiral

Draw a card. You may put a land card from your hand onto the battlefield.

Seedborn Muse

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

Mystic Snake

Flash
When Mystic Snake enters, counter target spell.

Harrow

As an additional cost to cast this spell, sacrifice a land.
Search your library for up to two basic land cards, put them onto the battlefield, then shuffle.

Callidus Assassin

Flash
Polymorphine — You may have Callidus Assassin enter tapped as a copy of any creature on the battlefield, except it has "When this creature enters, destroy up to one other target creature with the same name as this creature."

Cunning Nightbonder

Flash
Spells with flash you cast cost {1} less to cast and can't be countered.

Aboleth Spawn

Flash
Ward {2}
Probing Telepathy — Whenever a creature entering under an opponent's control causes a triggered ability of that creature to trigger, you may copy that ability. You may choose new targets for the copy.

Wavebreak Hippocamp

Whenever you cast your first spell during each opponent's turn, draw a card.

Mocking Doppelganger

Flash
You may have Mocking Doppelganger enter as a copy of a creature an opponent controls, except it has "Other creatures with the same name as this creature are goaded." (They attack each combat if able and attack a player other than you if able.)

Rewind

Counter target spell. Untap up to four lands.

Stunt Double

Flash
You may have Stunt Double enter as a copy of any creature on the battlefield.

Damia, Sage of Stone

Deathtouch
Skip your draw step.
At the beginning of your upkeep, if you have fewer than seven cards in hand, draw cards equal to the difference.

Venser, Shaper Savant

Flash
When Venser, Shaper Savant enters, return target spell or permanent to its owner's hand.