msem-instigator

{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.

{3}{B}, {T}: Choose a card name. Target player reveals cards from the top of their library until they reveal a card with the chosen name. If they do, put the revealed cards into their graveyard. Otherwise, they shuffle their library.

Inquisitor's Chamber enters tapped.
{T}: Add {B}.
{B}{B}, {T}, Sacrifice another permanent: Draw a card.

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature gets +2/+3 and has lifelink.

Whenever a creature you control dies, Insidious Terror gets +1/+0 and gains menace until end of turn.

Target creature gets -3/-3 until end of turn.
Target creature gets -3/-3 until end of turn.

If a card would be put into your graveyard from anywhere, exile it instead.
If you would draw a card, return two cards from your graveyard to your hand instead. If you can't, you lose the game.

When Into the Lion's Den enters, target opponent reveals their hand. You choose a nonland card from it and exile that card until Into the Lion's Den leaves the battlefield.

Target player sacrifices a nontoken creature and mills three cards.

Search your library for a Demon card or a black card with mana value 6 or greater, reveal it, put that card in your hand, then shuffle.

If you've lost life this turn, you may cast this spell as though it had flash.
Irate Retribution deals X damage to each creature and each planeswalker. You gain X life.

Whenever a creature you control leaves the battlefield, if it had counters on it, you may put one of those counters on Ironpact Marauder.
{1}{B}, Remove two counters from Ironpact Marauder: You draw a card and you lose 1 life.

Deathtouch
When Jade Empire Outlaw enters, surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Menace
Jara Champion can only attack or block alone.
Whenever one or more players lose life for the first time each turn, put a +1/+1 counter on Jara Champion.

When Jara Disciplinarian enters, each player sacrifices a creature.

Bloodprice {B}{B}{B}{B} (You may cast this card by sacrificing a creature and paying its bloodprice.)
Lifelink, haste
Sacrifice another Demon: Jejun, Dark Hunter gains flying and indestructible until end of turn.

Return target creature card from your graveyard to your hand. Catalyze. (The next spell you cast this turn costs {1} less to cast.)
Flashback {3}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Menace, lifelink
Whenever Jonah of the Spellbane deals combat damage to a player, destroy target creature or planeswalker, then scry 1.

When Journey through Uwaito enters, draw a card, then choose a creature card name.
Whenever a creature you control with the chosen name dies, each opponent discards a card.

Return target creature card from a graveyard to the battlefield. Then if that card wasn't put into a graveyard from the battlefield this turn, exile it.

Target player sacrifices a legendary creature or planeswalker.

Return target creature card from your graveyard to your hand. (Then exile this card. You may cast the creature later from exile.)

Menace
Vanguard — Whenever a creature you control attacks alone, it gets +1/+1 until end of turn for each creature card in your graveyard.

Flying
When Kai'Dwo, Eternal Ravager enters, create seven Idol tokens. (They're artifacts with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)
Whenever you sacrifice an Idol, each opponent sacrifices a creature.