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.

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.)

Deathtouch
When Kaneh Assassin enters, judge another target creature you control. (Honor it by putting a +1/+1 counter on it or condemn it by sacrificing it to draw a card.)

When Leyline Invoker enters and at the beginning of your upkeep, you may mill two cards.
{5}{B}, {T}, Sacrifice Leyline Invoker: Return target creature card from your graveyard to the battlefield. This ability costs {1} less to activate for each creature card in your graveyard.

Lifelink
{B}, Sacrifice Lostrite Evoker: Add {B}{B}{B}.

Flying
Whenever an opponent discards a card, put a +1/+1 counter on Nightbane Specter.
Whenever Nightbane Specter deals combat damage to a player, that player discards a card.

Whenever Organ Scavenger perseveres, each opponent loses 2 life. (A creature perseveres when it survives damage.)

Flying
Wither (This deals damage to creatures in the form of -1/-1 counters.)

Whenever you cast an instant or sorcery spell, each opponent loses 1 life.
Attain {3}{B} ({3}{B}: Transform this. Spend at least three colors of mana to activate this, and only as a sorcery.)

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

Whenever a creature dealt damage by Slave Child this turn dies, you may pay {B}. If you do, transform Slave Child.

Flying, lifelink
Morph {4}{B}
When Soul Cajoler is turned face up, manifest the bottom card of your library. (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.)

Whenever Spirit of Infamy attacks, post a bounty on target creature. (Put a bounty counter on that creature. It has “When this creature dies, each opponent draws a card” as long as it has a bounty counter on it.)
Spirit of Infamy gets +2/+0 for each bounty counter on it.

Deathtouch
Whenever you cast a spell, you may pay 2 life. If you do, that spell gains deathtouch. (If it becomes a permanent, it keeps deathtouch indefinitely.)

Whenever you gain life, each opponent loses 1 life.

Flying
Whenever another creature you control enters from a graveyard or you revive a creature token, Tomb Scavenger gets +2/+0 until end of turn.

Deathtouch
Menagerie — When Venomfrill Familiar enters, if there are five or more creature types among creatures you control, you may destroy target creature or planeswalker.

Deathtouch
At the beginning of your end step, create a 1/1 black Rat creature token with “This creature can't block.”
{1}{B}, {T}, Sacrifice three other creatures: Each opponent discards a card and loses 2 life. You draw a card and gain 2 life.

Deathtouch

Menace, haste
As long as Arleigh, Spellblade Prodigy is tapped, the first spell you cast during each other player's turn costs {U/R} less to cast. This effect reduces only the amount of colored mana you pay. (For example, if you cast a spell with mana cost {1}{R}, it costs {1} to cast.)

Rhapsody {4}{R}{R} (Pay {4}{R}{R} to cast this as a 4/4, or as a sorcery to make it become a 4/4.)
Trample
Whenever Attuned Slayer deals combat damage to a player, exile that many cards from the top of your library. You may play those cards this turn.

Creatures you control that have been dealt damage this turn get +2/+0.
When Bloodspawn enters, it deals 1 damage to target creature you control.

{T}: Add one mana of any color. Spend this mana only to cast an instant or sorcery spell.

Whenever one or more cards are put into an opponent's graveyard from their hand or library, Cackling Tormentor deals 2 damage to any target.

First strike, haste
Play with the top card of your library revealed.
{1}{R}: Darlene gets +1/+0 until end of turn.
Whenever Darlene deals damage to a player, if the top card of your library has mana value equal to the damage dealt, you may cast it without paying its mana cost.