msem-instigator

Counter target spell. If that spell is countered this way, put it into its owner's hand instead of into that player's graveyard. That player mills three cards.

{1}, {T}: Draw a card, then exile a card from your hand face down until Cluttered Study leaves the battlefield. (It returns to your hand.)
{3}, {T}: Shuffle Cluttered Study into its owner's library.

Flash
When Cocky Bladesinger enters, it gains first strike, lifelink, and haste until end of turn.

Whenever Cocky Delinquent is dealt damage, you gain that much life and Cocky Delinquent deals that much damage to up to one target creature or planeswalker you don't control.

For each permanent type, choose up to one target permanent of that type. Exile each of those permanents, then return them to the battlefield under your control. They gain haste until end of turn. At the beginning of your next end step, those permanents' owners gain control of them.

When Cognitive Fumigator enters, target opponent reveals their hand. You may choose a nonland card from it and exile that card. If you do, that player draws a card.
Recite {2}{U} (You may cast this creature from your graveyard for its recite cost. If you do, exile it when it enters or if it would leave the battlefield.)

Creatures have “Whenever this creature attacks or blocks, it fights another target creature.”

Whenever a land enters, Collapsing Realities deals 2 damage to each player.

Whenever you draw a card, you may exile the top card of your library.
{3}{U}{U}, Sacrifice Collector of Memories: Shuffle your hand into your library, then put each card exiled with Collector of Memories into its owner's hand.

Exile the top two cards of your library. You may play those cards until the end of your next turn. Whenever you play one of those cards, rouse 1. (Put a +1/+1 counter on a permanent you control. If it isn't a creature, tap it and it becomes a 0/0 creature in addition to its other types.)

Whenever a -1/-1 counter is put on a creature you control, you gain 1 life.
{1}{B}, Pay 1 life: Untap target Cleric. You may remove a -1/-1 counter from that creature.

Adorned — Commoners' Favored gets +2/+2 as long as it's equipped and/or enchanted.

Bleed {2}{B} (You may cast this spell for its bleed cost if an opponent has lost life this turn.)
Destroy target creature. Its controller loses 2 life.

Whenever a player casts a spell, each opponent mills a card.

When Compose from Dreams enters, you may cast any number of cards named Fatigue from your hand and graveyard without paying their mana costs.
Whenever you cast a spell, each opponent loses 1 life. Then you may draw a card if that spell wasn't cast from your hand. Then add {U}{B}{R} if you don't own that spell.

When Compulsion's Voice enters, gain control of target permanent until end of turn. Untap that permanent. It gains haste until end of turn.
Recite {1}{U}{R} (You may cast this creature from your graveyard for its recite cost. If you do, exile it when it enters or if it would leave the battlefield.)

When Compulsory Studies enters, exile target creature until Compulsory Studies leaves the battlefield. Each player draws a card.

Each player draws a card, then target player mills X cards, where X is the number of cards players have drawn this turn.

At the beginning of combat on your turn, you lose 1 life and rouse 1. (Put a +1/+1 counter on a permanent you control. If it isn't a creature, tap it and it becomes a 0/0 creature in addition to its other types.)

Other Knight creatures you control get +1/+1.

Draw a card, then copy target activated or triggered ability you don't control. You may choose new targets for the copy.
Exile Confirm Hypothesis.

Abound. Then search your library for a creature, instant, or sorcery card, reveal it, put it into your hand, then shuffle. (To abound, you may cast a spell that costs less than this from your hand without paying its mana cost.)

Whenever you cast an Aura spell, nourish 1. (To nourish 1, either put a +1/+1 counter on this creature or create a 1/1 white Citizen creature token.)

Destroy all noncreature, nonland permanents.

When Conniving Brigand enters, draw a card.