Nightmare Sower

Flying, lifelink
Whenever you cast a spell during an opponent's turn, put a -1/-1 counter on up to one target creature.

Glamermite

Flash
Flying
When this creature enters, choose one —
• Tap target creature.
• Untap target creature.

Rimefire Torque

As this artifact enters, choose a creature type.
Whenever a permanent you control of the chosen type enters, put a charge counter on this artifact.
{T}, Remove three charge counters from this artifact: When you next cast an instant or sorcery spell this turn, copy it. You may choose new targets for the copy.

Flitterwing Nuisance

Flying
This creature enters with a -1/-1 counter on it.
{2}{U}, Remove a counter from this creature: Whenever a creature you control deals combat damage to a player or planeswalker this turn, draw a card.

Unwelcome Sprite

Flying
Whenever you cast a spell during an opponent's turn, surveil 2. (Look at the top two cards of your library. You may put any number of them into your graveyard and the rest on top of your library in any order.)

Getting

Glen Elendra Guardian

Flash
Flying
This creature enters with a -1/-1 counter on it.
{1}{U}, Remove a counter from this creature: Counter target noncreature spell. Its controller draws a card.

Glamer Gifter

Flash
Flying
When this creature enters, choose up to one other target creature. Until end of turn, that creature has base power and toughness 4/4 and gains all creature types.

Voracious Tome-Skimmer

Flying
Whenever you cast a spell during an opponent's turn, you may pay 1 life. If you do, draw a card.

Temporal Cleansing

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
The owner of target nonland permanent puts it into their library second from the top or on the bottom.

Swat Away

This spell costs {2} less to cast if a creature is attacking you.
The owner of target spell or creature puts it on their choice of the top or bottom of their library.

Swamp

Illusion Spinners

You may cast this spell as though it had flash if you control a Faerie.
Flying
This creature has hexproof as long as it's untapped. (It can't be the target of spells or abilities your opponents control.)

Wild Unraveling

As an additional cost to cast this spell, blight 2 or pay {1}. (To blight 2, put two -1/-1 counters on a creature you control.)
Counter target spell.

Dream Seizer

Flying
When this creature enters, you may blight 1. If you do, each opponent discards a card. (To blight 1, put a -1/-1 counter on a creature you control.)