msem-instigator

Frenzy 1 (Whenever this creature attacks and isn't blocked, it gets +1/+0 until end of turn.)
Whenever Trading Traitor deals combat damage to a player, you lose life equal to the number of unblocked attacking creatures you control and draw that many cards.

I, II — Mill two cards. You gain 2 life. (Put the top two cards of your library into your graveyard.)
Discovery — During each of your turns, you may cast a permanent spell from your graveyard.

You draw a card, lose 2 life, then create a Vial token. (It's an artifact with “{1}, Sacrifice this and another permanent: Draw a card. Activate only during your turn.”)

Destroy target creature with power less than or equal to the number of creature cards in your graveyard.

At the beginning of your end step, you may mill a card.
{3}{B}, Exile two cards from your graveyard: Target player loses 2 life.

When Trainer of the Abyss dies, create a 1/1 black Demon Hound creature token with deathtouch.

All creatures get -2/-2 until end of turn. Remove two loyalty counters from each planeswalker.

Kicker—Sacrifice a creature. (You may sacrifice a creature in addition to any other costs as you cast this spell.)
You draw two cards and you lose 2 life. If this spell was kicked, you draw four cards and you lose 4 life instead.

{3}{B}, Discard a card: Each opponent loses 2 life and you gain 2 life.
At the beginning of your upkeep, if there are five or more creature types among cards in your graveyard, you lose 1 life and draw a card.

Destroy target creature with no counters on it and no permanents attached to it.

Bleed {1}{B} (You may cast this spell for its bleed cost if an opponent lost life this turn.)
Deathtouch
Treacherous Informant enters with two +1/+1 counters on it if you paid its bleed cost.
You may cast spells for their bleed costs if you lost life this turn.

{B}: Treacherous Shade gets +1/+1 until end of turn.
{1}{B}{B}: Treacherous Shade gets +3/+3 until end of turn.

Destroy target creature. Mill a number of cards equal to its power.

When Treacherous Warden enters, search your library for a card, put into your graveyard, then shuffle.
Whenever a creature enters from your graveyard, each opponent loses 2 life and you gain 2 life.

{2}{B}, Sacrifice a creature: Draw a card.

When Trenchbottom Mariners enters, you lose 3 life, mill three cards, and create a Treasure token.
Whenever Trenchbottom Mariners attacks, you may cast a permanent card from your graveyard by sacrificing another artifact in addition to paying its costs.

Each player sacrifices a creature. (Then exile this card. You may cast the artifact later from exile.)

{2}, Sacrifice another creature: Create an Idol token. (It's an artifact with “{1}, Sacrifice this artifact: Put a +1/+1 counter on target creature. Activate only as a sorcery.”)

Deathtouch

Return all creature cards from your graveyard to the battlefield, then exile all but one of them.

Once each turn, when you search your library, you may add {B}{B}.

Whenever a creature dealt damage by Truth Extractor this turn dies, investigate. (Create a colorless Clue artifact token with “{2}, Sacrifice this artifact: Draw a card.”)

Enchant player
At the beginning of enchanted player's upkeep, they choose one —
• That player reveals their hand and discards a card.
• That player discards a card at random.

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature gets +1/+0 and has deathtouch. (Any amount of damage it deals to a creature is enough to destroy it.)

Menace
Whenever an opponent discards a card, monstrosity 2. (If this creature isn't monstrous, put two +1/+1 counters on it and it becomes monstrous.)