msem-instigator

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.

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.

Search target player's library for a card and exile it. Then that player shuffles.

Whenever a creature you control dies, you may put a +1/+1 counter on target creature you control.

Flying
Attain {4}{B} ({4}{B}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

Whenever Inishtu, Desert Healer enters or attacks, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)
At the beginning of your upkeep, if seven or more cards are in your graveyard, you may transform Inishtu.

Indestructible
{2}{B}, Exile two cards from your graveyard: Each opponent loses 2 life and you gain 2 life.

When Ink Seer dies, you draw a card, lose 1 life, and create a Treasure token.

At the beginning of your end step, if you lost 2 or more life this turn, create a 1/1 black Bird creature token with flying. If you lost 4 or more life this turn, instead create a 3/3 black Cat creature token with deathtouch. If you lost 6 or more life this turn, instead create a 5/5 black Golem creature token with trample.

As an additional cost to cast this spell, sacrifice a creature.
Enchant creature
Enchanted creature gets +4/+4, has flying, and is a Demon in addition to its other types.

{2}{B}, Sacrifice Innocuous Sidekick and another creature: Create a 4/4 black Horror creature token with menace. Activate only as a sorcery.

[+1]: Each opponent puts a -1/-1 counter on a creature they control.
[–1]: Exile target card in a graveyard. You gain life equal to its mana value.
[–6]: Choose a number. You draw that many cards and you lose that much life.