msem-instigator

Choose a card in your graveyard. Search your library for a card with the same name as that card, reveal it, put it into your hand, then shuffle.

Each opponent sacrifices a creature or planeswalker. If you own a foretold card in exile, you gain 4 life.

Enchant creature
Enchanted creature gets +2/+2 and has trample and indestructible.

Whenever a face-down creature you control attacks, defending player loses 1 life.
{2}, Discard a card: Manifest the bottom card of your library. Activate only once each turn. (To manifest a card, put it onto the battlefield face down as a 2/2 creature. Turn it face up any time for its mana cost if it's a creature card.)

Defender
When Immured Fiend enters, target opponent discards two cards.

At the beginning of your upkeep, if you don't control any Imps, you may pay {B}. If you do, create a 1/1 black Imp creature token.
Sacrifice a creature: Each opponent loses 1 life.

As an additional cost to cast this spell, discard a nonland card.
All creatures get -X/-X until end of turn, where X is the discarded card's mana value.

All creatures get -2/-2 until end of turn.
Civilized — Instead only creatures your opponents control get -2/-2 until end of turn if you control an artifact, a creature, and an enchantment.

Civilized — At the beginning of your upkeep, if you control an artifact, a creature, and an enchantment, you draw a card and you lose 1 life.

First strike
Art of war — At the beginning of your end step, if Imperial Kensai dealt damage to an opponent this turn, you may pay 1 life. If you do, put a +1/+1 counter on Imperial Kensai.

Create a 2/2 black Horror creature token.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

Destroy target tapped creature. You gain 2 life.

Each opponent loses 1 life and you gain 1 life. Surveil 2.
Compose (Then if you cast this from your hand, exile it and create a Saga token with “r3—You may cast a copy of this card from exile without paying its mana cost.”)

Death knell — Return an Aura card with mana value 5 or less from your graveyard to the battlefield. (As a creature you control dies, trigger one death knell of that creature or another permanent you control.)
As long as Inconspicuous Otter is enchanted or equipped, he's a 3/4 legendary Otter Rogue named Agent O and has menace.

Menace
At the beginning of your end step, if you gained or lost life this turn, put a -1/-1 counter on up to one target creature.

Target creature gets -1/-1 until end of turn.
Threshold — You may destroy that creature instead if seven or more cards are in your graveyard.

This spell costs {1} less to cast for each creature and/or planeswalker card in your graveyard.
Return target creature or planeswalker card from your graveyard to the battlefield.

Enchant opponent
Creatures enchanted player controls get -2/-2.
Whenever enchanted player casts a noncreature spell, they lose 2 life and you gain 2 life.

When Inexperienced Martyr dies, each opponent loses 1 life.

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature gets -1/-1.
Whenever enchanted creature attacks, its controller loses 2 life.

Deathtouch
Whenever Infected Null attacks, each player loses 1 life.

When Infectious Corpse dies, each player loses 2 life.

Lifelink
Whenever Infectious Ego enters or attacks, exile the top card of target opponent's library. If it's a land card, that player gets a poison counter. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast that spell.

At the beginning of each end step, if a player lost 5 or more life this turn, create a 5/5 black Demon creature token with flying.

When Infested Goblin dies, choose target creature. At the beginning of your next upkeep, that creature's controller sacrifices it.