msem-instigator

{1}{G}, {T}, Sacrifice another nontoken creature: Create two tokens that are copies of the sacrificed creature, except they're 0/1. Activate only as a sorcery.

{T}, Sacrifice another permanent: Add one mana of any color.
At the beginning of your end step, if you're horrific, put a +1/+1 counter on target creature. (You're horrific as long as you've sacrificed a permanent or discarded a card this turn.)

At the beginning of your end step, if you own a card in exile, create a 1/1 white Spirit creature token with flying.

Whenever a creature enters the battlefield under your control for the first time each turn, you may sacrifice it. If you do, exile cards from the top of your library until you exile a creature card. Put that card onto the battlefield.

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.

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.)

Menace
At the beginning of your end step, He of All Hallow's Eve deals damage equal to its power to you unless you're horrific. (You're horrific as long as you've sacrificed a permanent or discarded a card this turn.)

Hellfire Caverns enters the battlefield tapped.
{T}: Add {R}.
{2}{R}: Until end of turn, Hellfire Caverns becomes a 3/3 Devil creature with menace. Activate only if you're horrific.

You may put a permanent card from your hand onto the battlefield.
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.)

If another creature you control would die, exile it instead.
When John Furo, the Unfortunate dies, until your next end step, you may play cards exiled with John Furo.

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.

Whenever you cast a spell from exile, copy that spell. You may choose new targets for the copy.
{B}, Discard a card: When you cast your next spell from your hand this turn, it gains rerun. Activate this ability only once each turn. (Exile it as it resolves if you cast it from your hand. Whenever a creature you control dies, you may cast that card from exile without paying its mana cost.)

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.)

Lifelink
If a creature or planeswalker would die, instead exile it and put a +1/+1 counter on Librarian of Whispers.

When Lisa, the Daughter enters the battlefield, create Mother, a legendary 4/1 black Demon creature token with flying and “This creature can't block.”
If a source would deal damage to Lisa while you control a Demon creature, instead that damage is dealt to a Demon creature you control of your choice.

Living Broadcast can't block.
Whenever you cast a spell from exile, you may return Living Broadcast from your graveyard to your hand.

Lost Station enters the battlefield tapped.
{T}: Add {U}.
{U}{U}: Until end of turn, Lost Station becomes a 2/2 Horror creature with “This creature can't be blocked.” Activate only if you're horrific.

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.

Haste
Whenever Malformed Mongrel deals combat damage to a player, discard a card.

Other creatures you control get +2/+0 and have menace.
Whenever another creature you control dies, if it wasn't sacrificed, sacrifice a creature.

Misty Churchyard enters the battlefield tapped.
{T}: Add {W}.
{1}{W}{W}: Until end of turn, Misty Churchyard becomes a 1/4 Cleric creature with “Whenever this creature is dealt damage, put that many +1/+1 counters on it.” Activate only if you're horrific.

Whenever Morbid Mimic enters the battlefield or attacks, exile up to one target creature card from a graveyard.
Morbid Mimic has all activated abilities of cards exiled with it.