Alela, Cunning Conqueror

Flying
Whenever you cast your first spell during each opponent's turn, create a 1/1 black Faerie Rogue creature token with flying.
Whenever one or more Faeries you control deal combat damage to a player, goad target creature that player controls.

Academy Loremaster

At the beginning of each player's draw step, that player may draw an additional card. If they do, spells they cast this turn cost {2} more to cast.

Blightwing Bandit

Flying, deathtouch
Whenever you cast your first spell during each opponent's turn, look at the top card of that player's library, then exile it face down. You may play that card for as long as it remains exiled, and mana of any type can be spent to cast it.

Stinging Lionfish

Whenever you cast your first spell during each opponent's turn, you may tap or untap target nonland permanent.

Dreamspoiler Witches

Flying
Whenever you cast a spell during an opponent's turn, you may have target creature get -1/-1 until end of turn.

Naiad of Hidden Coves

During turns other than yours, spells you cast cost {1} less to cast.

Nymris, Oona's Trickster

Flash
Flying
Whenever you cast your first spell during each opponent's turn, look at the top two cards of your library. Put one of those cards into your hand and the other into your graveyard.

Wavebreak Hippocamp

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

Slitherwisp

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

Dream Spoilers

Flying
Whenever you cast a spell during an opponent's turn, up to one target creature an opponent controls gets -1/-1 until end of turn.