msem-instigator

Exile target creature. Return that creature to the battlefield under its owner's control at the beginning of the next end step.
Rerun (If you cast this from your hand, exile it as it resolves. Whenever a creature you control dies, you may cast this card from exile without paying its mana cost.)

Creatures can't attack you or planeswalkers you control unless their controller pays 2 life for each of those creatures.

Players can't sacrifice creatures to cast spells or activate abilities unless that player sacrifices an additional creature. The same is true for discarding cards and paying life.

Flying
When Planchette Poltergeist enters the battlefield, you may exile target creature. Its owner may cast it from exile for as long as it remains exiled.

Choose a creature. Exile the rest.

At the beginning of each end step, create X 1/1 white Spirit creature tokens with flying, where X is the number of nontoken creatures that died this turn.

As long as you control exactly one creature, no more than one creature can attack or block each combat.

Create an 8/8 blue Kraken creature token with hexproof.
Rerun (If you cast this from your hand, exile it as it resolves. Whenever a creature you control dies, you may cast this card from exile without paying its mana cost.)

Whenever a creature you control deals combat damage to a player, you may sacrifice it. If you do, draw cards equal to that creature's power.

Counter target spell if it wasn't cast from a player's hand.

When Demented Brainiac enters the battlefield and at the beginning of your upkeep, each opponent mills two cards.
{U}, Sacrifice Demented Brainiac: Exile each opponent's graveyard. Until end of turn, you may cast instant and sorcery spells exiled this way, and you may spend mana as though it were mana of any color to cast them.

Draw two cards.
Rerun (If you cast this from your hand, exile it as it resolves. Whenever a creature you control dies, you may cast this card from exile without paying its mana cost.)

Put target creature on the bottom of its owner's library. That player reveals cards from the top of their library until they reveal a creature card, then puts all cards revealed this way into their graveyard.

Spells your opponents cast that target Sheltered Snowman cost {2} more to cast.
Whenever you cast a spell from exile, put a +1/+1 counter on Sheltered Snowman. It can't be blocked this turn.

You may have Snowfield Doppelganger enter the battlefield as a copy of any creature on the battlefield, except it has “While a player is choosing targets as part of casting a spell, that player must choose at least one other creature that shares a name with this creature if able.”

Look at the top five cards of your library. You may reveal a nonland card from among them. If you do, put that card into your hand and cast a copy of it without paying its mana cost. Put the rest into your graveyard.

Discard a card: Unseen Maniac gets +1/+1 and can't be blocked this turn.
Whenever Unseen Maniac deals combat damage to a player, draw a card.

Whenever an opponent casts a spell, that player mills X cards, where X is that spell's mana value.

Flash
When Wiretapper enters the battlefield, choose one —
• Exile target spell. For as long as that card remains exiled, its owner may play it. A spell cast this way costs {2} more to cast.
• Create a copy of the card with target spell's name. You may cast the copy. (You still pay its costs.)

At the beginning of your end step, if you're horrific, you draw a card and you lose life equal to the number of cards in your hand. (You're horrific as long as you've sacrificed a permanent or discarded a card this turn.)

Bedfellow can't block or be blocked.
Exile two cards from your graveyard: Bedfellow gets +1/+1 until end of turn.

Target opponent sacrifices a creature.
Rerun (If you cast this from your hand, exile it as it resolves. Whenever a creature you control dies, you may cast this card from exile without paying its mana cost.)

Target player discards two cards.
Rerun (If you cast this from your hand, exile it as it resolves. Whenever a creature you control dies, you may cast this card from exile without paying its mana cost.)

Return target creature card from a graveyard to the battlefield. Then if that card wasn't put into a graveyard from the battlefield this turn, exile it.

Flying
At the beginning of your end step, put a +1/+1 counter on Lepidopteradator if you're horrific. Otherwise, sacrifice it. (You're horrific as long as you've sacrificed a permanent or discarded a card this turn.)