msem-instigator

Create a 5/3 black Horror creature token.
Flashback {1}{B}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Pressure {3}{B}{B} (You may cast this spell for its pressure cost if seven or more cards are in your graveyard.)
Each player sacrifices a creature. Put a creature card from a graveyard onto the battlefield under your control.

Target opponent shuffles a card from their hand into their library.

Desecrate (When this creature enters, you may sacrifice an artifact or land.)
When Back-Alley Vandal desecrates a permanent, put a +1/+1 counter on Back-Alley Vandal.

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)

Mark (Whenever this creature attacks, mark target creature until end of turn.)
Whenever Backalley Silencer deals combat damage to a player, destroy target marked creature.

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

Deathtouch
When Backstage Comic enters, target player discards a card.

Lifelink
Whenever Backstage Prompter deals combat damage to a player, put a +1/+1 counter on it.

Exile target creature or planeswalker. You gain 4 life.

Scry X, then purge X times. You lose X life. (To purge, exile two cards that share a type from graveyards. If you do, draw a card.)

When Bal's Descent enters, each player sacrifices a creature, discards two cards, and mills three cards.
{1}{B}{B}: Transform Bal's Descent. Activate only if your fealty to Swamps is five or greater.

Indestructible
You may play cards from your graveyard.
If you would draw one or more cards, mill that many cards instead.
If a card would be put into your graveyard from anywhere other than your library, exile it instead.

Flying, deathtouch

Whenever equipped creature attacks, it gains deathtouch until end of turn.
Sacrifice Bandit's Dagger: Target player dealt damage by equipped creature this turn reveals their hand. You choose a nonland card from it. That player discards that card.
Equip {2}

Destroy target face-up creature.

Engorge (As this enters, mill three cards, then exile a card from among the milled cards.)
When Bane of Sanity enters, if it engorged a creature card, target player discards two cards.

As an additional cost to cast this spell, sacrifice a creature.
All creatures get -X/-X until end of turn, where X is the sacrificed creature's power.

When Baneblade Stalker enters, proliferate. (Choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)

Exile target creature or planeswalker and all other creatures its controller controls with the same name as that permanent. Search its controller's graveyard, hand, and library for any number of nonland cards with the same name as that permanent and exile them. Then that player shuffles.

{2}{B}, Exile Barbed Cocoon from your graveyard: Create two 1/1 green Insect creature tokens. Activate only as a sorcery.

Barbed Reef enters tapped. When it does, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this, then you may put that card into your graveyard.)
{T}: Add {B}.
{4}{B}: Barbed Reef becomes a Jellyfish creature. (This effect lasts indefinitely.)

Barren Boneyard enters tapped.
{T}: Add {B}.
{2/B}{2/B}: Barren Boneyard becomes a 2/3 black Elemental creature with deathtouch until end of turn. It's still a land.

Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever Barrow Banshee deals combat damage to an opponent, that player discards a card at random.

When Battery Courier dies, lose 2 life.