msem-instigator

At the beginning of your upkeep, you may sacrifice another creature. If that creature had mana value 2 or greater, create a 3/2 colorless Horror creature token. Otherwise, create a 1/1 colorless Human creature token.
Whenever you create a creature token, you may pay 2 life. If you do, put a menace counter on it.

Whenever another creature you control dies, each opponent loses 1 life and you gain 1 life. Then you may pay {B}. If you do, Disciple of Myriad Fates becomes a copy of that creature, except it has this ability.

When Duskling Stalker dies, if it didn't have any counters on it, return it to the battlefield with your choice of a deathtouch, lifelink, or +1/+1 counter on it.

Choose one —
• Exile all creature tokens.
• Exile target creature or planeswalker.
• Each opponent exiles a card from their hand and loses 2 life.

Create a 3/2 colorless Horror creature token. All other creatures get -3/-3 until end of turn.

Choose any number of target creature and/or planeswalker cards in your graveyard. Return one of them to the battlefield and put the rest on top of your library in any order.

When Goremound enters, target creature you don't control gets -3/-3 until end of turn. All other creatures you don't control with the same name as that creature get -1/-1 until end of turn.
Evoke {1}{B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Flash
When Gravetiller enters, you may exile target creature or planeswalker card from a graveyard. If it had mana value 4 or less, you may return it to its owner's hand. Otherwise, you may shuffle it into its owner's library.
Evoke {B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Once each turn, when Groz, the Nightshaper enters or you attack with one or more Horrors, you may return target nonlegendary creature card from your graveyard to your hand. Then if Groz isn't a token, create a token that's a copy of that creature card.
{2}{B}{B}, Discard Groz: Create a token that's a copy of Groz, the Nightshaper, except it's 4/4 and isn't legendary. Activate only as a sorcery.

Marrowskitter can't block and can't be blocked.
{3}{B}{B}: Return Marrowskitter from your graveyard to the battlefield. Create a token that's a copy of it.

Rattlecage Terror enters tapped.
{1}{B}: Return Rattlecage Terror from your graveyard to your hand. When you do, another target creature card with mana value 3 or less in your graveyard gains this activated ability until end of turn, except it costs {1} more to activate.

Destroy target creature with mana value 2 or less. If it was a token, you gain 2 life.

Target player mills a card. Create a 3/2 colorless Horror creature token. Put a decayed counter on it. (It can't block. When it attacks, sacrifice it at end of combat.)

Once each turn, when you cast a noncreature spell, create a 1/1 colorless Human creature token. Put a prowess counter on it.

[+1]: Creatures you control get +1/+0 and gain haste until end of turn.
[0]: Bennett Brooks deals 2 damage to each opponent. If you have an insight counter, create two Treasure tokens.
[0]: You get an insight counter.
[–2]: Sacrifice an artifact. If you do, return target artifact card from your graveyard to the battlefield.

Blazing Exultation deals 3 damage to any target.
{2}{R}: Shuffle Blazing Exultation and up to one other instant or sorcery card from your graveyard into your library.

Flying, menace, haste
When Bloodfiend Ravager enters, it deals 2 damage to any target. If a permanent dealt damage this way would die this turn, exile it instead.
Evoke {1}{R} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Menace
Sacrifice another creature: Corpulent Gibberer deals 1 damage to any target.
Evoke {1}{R} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

If an effect would create one or more tokens under your control, it creates twice that many of those tokens instead, except the additional tokens are named Ingenious Idea.
At the beginning of your end step, exile each token you control named Ingenious Idea.

Enchant creature
Enchanted creature gets +1/+0 and has menace and haste.
You may cast Empty the Magazine from your graveyard by paying {3}{R} rather than paying its mana cost.

Once each turn, when Eruq, the Flamebearer enters or you attack with one or more Horrors, you may have Eruq deal 2 damage to each opponent. Then if Eruq isn't a token, gain control of target creature an opponent controls until end of turn. Tap it. It's attacking its controller.
{2}{R}{R}, Discard Eruq: Create a token that's a copy of Eruq, the Flamebearer, except it's 4/4 and isn't legendary. Activate only as a sorcery.

Choose one. If you attacked with a creature with mana value 5 or greater this turn, you may choose any number instead.
• Destroy target artifact.
• Destroy target land.
• Fate of the World deals 3 damage divided as you choose among one, two, or three targets.

Menace
Whenever an opponent activates an ability that isn't a mana ability, Flensing Tormentor deals 1 damage to that player.

Flamebearer's Domain enters tapped.
{T}: Add {R}.

{T}: Keepers of the Reach deals 1 damage to each opponent.
{2}{R}, {T}: Keepers of the Reach deals 3 damage to each opponent. Activate only if you control a permanent with mana value 5 or greater.