msem-instigator

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.

Whenever an opponent activates an ability of a nonland permanent, destroy that permanent.
{3}{U}{B}{R}: Exile target creature or planeswalker card in a graveyard. Create a token that's a copy of it.

(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.

Rather than pay the mana cost for a spell, its controller may discard a card that shares a color with that spell.
Whenever an opponent casts a spell, counter that spell unless they pay 5 life.

(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.

Deathtouch
Whenever you lose life, you may cast target black noncreature card in your graveyard this turn. If it would be put into a graveyard from anywhere this turn, exile it instead.
Whenever you gain life for the first time each turn, create a 1/1 black Actor creature token.

Target player discards a card and gets a poison counter.
Coalesce {4}{B}{B} (You may cast this from your graveyard for {4}{B}{B}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

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.

Flying
Whenever one or more other creatures die for the first time each turn, journey. (To journey, exile the top card of your library face up. Whenever a creature you control deals combat damage to an opponent, put a journeyed card you own into your hand.)

(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.

The Urchin King's power and toughness are each equal to the number of cards in all graveyards.
Sacrifice a creature: The Urchin King gains lifelink and indestructible until end of turn.

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.

{1}{B}: Target Knight or Soldier you control gains deathtouch until end of turn.

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.)

When Thoughtslick Engineer enters, each player discards a card at random.

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.