msem-instigator

Death knell — All creatures get -1/-1 until end of turn. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)
{B}, Sacrifice a creature: Choose a card in your graveyard with mana value less than the sacrificed creature's mana value. You may cast it without paying its mana cost.

Whenever a creature an opponent controls dies, its controller loses 1 life.
At the beginning of each opponent's upkeep, put a -1/-1 counter on each creature that player controls.

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Return target creature card with mana value 2 or less from your graveyard to the battlefield.
II — Each opponent loses 2 life and you gain 2 life.
III — Return target creature card with mana value 2 or less from your graveyard to the battlefield.

(You may cast a legendary sorcery only if you control a legendary creature or planeswalker.)
Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.

When The Moon Rises enters, exile all opponent's graveyards.
At the beginning of your upkeep, each opponent loses 1 life.

Each player chooses a nonbasic card name, then searches each of their opponents' graveyards, hands, and libraries for any number of cards with the chosen name and exiles them. Each player shuffles, then draws a card for each card exiled from their hand this way.

(Transform this if it's not attached to a creature.)
Enchant creature you control
The Scourgebone Pact's rider gets +2/+1, has flying, lifelink and deathtouch, and can't dismount. (This still transforms into a creature if its rider leaves the battlefield.)

Return target creature card from your graveyard to the battlefield.
Reconstruct {4}{B}{B}{B} (You may cast this from your graveyard for its reconstruct cost reduced by the mana value of a permanent you sacrifice as you cast it this way. Then exile this.)

At the beginning of your upkeep, return target creature card from your graveyard to the battlefield.

Siphon (Each -1/-1 counter you put on your creatures up to their remaining toughness while casting this pays for {1}.)
Return target creature or planeswalker card from your graveyard to the battlefield. Each opponent loses 3 life.

Target opponent discards two cards. You create a 0/1 black Cultist creature token with “{1}{B}{B}, Sacrifice three Cultists: Create a 5/5 black Demon creature token.”

Choose two —
• Scry 3, then you may mill up to three cards.
• Each opponent loses 3 life.
• You draw a card and you lose 1 life.
• Return a creature card from your graveyard to your hand.

Target opponent reveals their hand. You choose a nonland permanent card from it. That player discards that card.

Equipped creature gets +2/+0 and has deathtouch.
Equip Rogue or Assassin {1}
Equip {3}

Search your library for a nonland card not named Thin the Veil, exile it, then shuffle. If it has mana value less than or equal to the number of card types among cards in your graveyard, you may cast it without paying its mana cost. If you don't, put it into your hand.

Purge, then you may pay 2 life. If you do, purge again. (To purge, exile two cards that share a type from graveyards. If you do, draw a card.)

Enchant creature
Enchanted creature gets +3/+1.

Reveal the cards in your library. Target opponent chooses three nonland cards with different names from it. You put the chosen cards into your hand. Then shuffle.

Target creature gets -3/-3 until end of turn. Its controller loses 3 life. You mill three cards.

Investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)
Flashback—{B}, Pay 2 life. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Each opponent sacrifices a creature or planeswalker.
Acquiesce (If you cast this spell from your hand, exile it as it resolves. When one or more creatures you control deal combat damage to an opponent, you may cast this card from exile without paying its mana cost.)

Return target creature card from your graveyard to the battlefield, then destroy target creature an opponent controls that doesn't share a creature type with it.

Foretell {1}{B} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)
Create two X/X black Zombie creature tokens with menace, where X is the number of nontoken creatures that died under your control this turn.

At the beginning of each end step, put a +1/+1 counter on equipped creature for each creature that died this turn.
Equip {1}

Target opponent reveals their hand. You choose a creature card from it. That player discards that card.