Thrill-Kill Assassin

Deathtouch
Unleash (You may have this creature enter with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)

Curse of the Cabal

Target player sacrifices half the permanents they control of their choice, rounded down.
Suspend 2—{2}{B}{B} (Rather than cast this card from your hand, you may pay {2}{B}{B} and exile it with two time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)
At the beginning of each player's upkeep, if Curse of the Cabal is suspended, that player may sacrifice a permanent of their choice. If the player does, put two time counters on Curse of the Cabal.

Silumgar Assassin

Creatures with power greater than Silumgar Assassin's power can't block it.
Megamorph {2}{B} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its megamorph cost and put a +1/+1 counter on it.)
When Silumgar Assassin is turned face up, destroy target creature with power 3 or less an opponent controls.

Dark Impostor

{4}{B}{B}: Exile target creature and put a +1/+1 counter on Dark Impostor.
Dark Impostor has all activated abilities of all creature cards exiled with it.

Garza's Assassin

Sacrifice Garza's Assassin: Destroy target nonblack creature.
Recover—Pay half your life, rounded up. (When another creature is put into your graveyard from the battlefield, you may pay half your life, rounded up. If you do, return this card from your graveyard to your hand. Otherwise, exile this card.)

Scarblade Elite

{T}, Exile an Assassin card from your graveyard: Destroy target creature.

Cruel Sadist

{B}, {T}, Pay 1 life: Put a +1/+1 counter on Cruel Sadist.
{2}{B}, {T}, Remove X +1/+1 counters from Cruel Sadist: It deals X damage to target creature.

Revel in Riches

Whenever a creature an opponent controls dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
At the beginning of your upkeep, if you control ten or more Treasures, you win the game.

Eat to Extinction

Exile target creature or planeswalker. Surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)

Dash Hopes

When you cast this spell, any player may pay 5 life. If a player does, counter Dash Hopes.
Counter target spell.

Nightshade Assassin

First strike
When Nightshade Assassin enters, you may reveal X black cards in your hand. If you do, target creature gets -X/-X until end of turn.
Madness {1}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Cabal Ritual

Add {B}{B}{B}.
Threshold — Add {B}{B}{B}{B}{B} instead if seven or more cards are in your graveyard.

Swamp

Withering Boon

As an additional cost to cast this spell, pay 3 life.
Counter target creature spell.

Pain's Reward

Each player may bid life. You start the bidding with a bid of any number. In turn order, each player may top the high bid. The bidding ends if the high bid stands. The high bidder loses life equal to the high bid and draws four cards.

Lethal Sting

As an additional cost to cast this spell, put a -1/-1 counter on a creature you control.
Destroy target creature.

Vampire's Bite

Kicker {2}{B} (You may pay an additional {2}{B} as you cast this spell.)
Target creature gets +3/+0 until end of turn. If this spell was kicked, that creature gains lifelink until end of turn. (Damage dealt by the creature also causes its controller to gain that much life.)

Oblivion's Hunger

Target creature you control gains indestructible until end of turn. Draw a card if that creature has a +1/+1 counter on it. (Damage and effects that say "destroy" don't destroy the creature.)

Agent of the Fates

Deathtouch
Heroic — Whenever you cast a spell that targets Agent of the Fates, each opponent sacrifices a creature of their choice.

Guul Draz Assassin

Level up {1}{B} ({1}{B}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 2-3
2/2
{B}, {T}: Target creature gets -2/-2 until end of turn.
LEVEL 4+
4/4
{B}, {T}: Target creature gets -4/-4 until end of turn.

Kiku, Night's Flower

{2}{B}{B}, {T}: Target creature deals damage to itself equal to its power.

Stronghold Assassin

{T}, Sacrifice a creature: Destroy target nonblack creature.

Zombie Assassin

{T}, Exile two cards from your graveyard and Zombie Assassin: Destroy target nonblack creature. It can't be regenerated.

Read the Bones

Scry 2, then draw two cards. You lose 2 life. (To scry 2, look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Grim Affliction

Put a -1/-1 counter on target creature, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Cabal Pit

{T}: Add {B}. Cabal Pit deals 1 damage to you.
Threshold — {B}, {T}, Sacrifice Cabal Pit: Target creature gets -2/-2 until end of turn. Activate only if seven or more cards are in your graveyard.

Hunter of Eyeblights

When Hunter of Eyeblights enters, put a +1/+1 counter on target creature you don't control.
{2}{B}, {T}: Destroy target creature with a counter on it.

Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Nekrataal

First strike
When Nekrataal enters, destroy target nonartifact, nonblack creature. That creature can't be regenerated.

Serpent Assassin

When Serpent Assassin enters, you may destroy target nonblack creature.

Doom Blade

Incremental Blight

Put a -1/-1 counter on target creature, two -1/-1 counters on another target creature, and three -1/-1 counters on a third target creature.

Urge to Feed

Target creature gets -3/-3 until end of turn. You may tap any number of untapped Vampire creatures you control. If you do, put a +1/+1 counter on each of those Vampires.

Massacre Girl

Menace
When Massacre Girl enters, each other creature gets -1/-1 until end of turn. Whenever a creature dies this turn, each creature other than Massacre Girl gets -1/-1 until end of turn.

Xathrid Slyblade

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
{3}{B}: Until end of turn, Xathrid Slyblade loses hexproof and gains first strike and deathtouch. (It deals combat damage before creatures without first strike. Any amount of damage it deals to a creature is enough to destroy it.)

Sol Ring

Virtus the Veiled

Partner with Gorm the Great (When this creature enters, target player may put Gorm into their hand from their library, then shuffle.)
Deathtouch
Whenever Virtus the Veiled deals combat damage to a player, that player loses half their life, rounded up.

Abyssal Hunter

{B}, {T}: Tap target creature. Abyssal Hunter deals damage equal to Abyssal Hunter's power to that creature.

Unliving Psychopath

{B}: Unliving Psychopath gets +1/-1 until end of turn.
{B}, {T}: Destroy target creature with power less than Unliving Psychopath's power.

Tsabo's Assassin

{T}: Destroy target creature if it shares a color with the most common color among all permanents or a color tied for most common. A creature destroyed this way can't be regenerated.

Unexpected Fangs

Put a +1/+1 counter and a lifelink counter on target creature.

Parting Thoughts

Destroy target creature. You draw X cards and you lose X life, where X is the number of counters on that creature.

Reign of Terror

Destroy all green creatures or all white creatures. They can't be regenerated. You lose 2 life for each creature that died this way.

Dismember

({B/P} can be paid with either {B} or 2 life.)
Target creature gets -5/-5 until end of turn.

Mer-Ek Nightblade

Outlast {B} ({B}, {T}: Put a +1/+1 counter on this creature. Outlast only as a sorcery.)
Each creature you control with a +1/+1 counter on it has deathtouch.

Witch's Vengeance

Creatures of the creature type of your choice get -3/-3 until end of turn.

Vendetta

Destroy target nonblack creature. It can't be regenerated. You lose life equal to that creature's toughness.

Grotesque Mutation

Target creature gets +3/+1 and gains lifelink until end of turn. (Damage dealt by the creature also causes its controller to gain that much life.)

Royal Assassin

Cabal Stronghold

{T}: Add {C}.
{3}, {T}: Add {B} for each basic Swamp you control.

Torment of Venom

Put three -1/-1 counters on target creature. Its controller loses 3 life unless they sacrifice another nonland permanent of their choice or discard a card.

Dark Ritual

Hired Poisoner

Rush of Vitality

Target creature gets +1/+0 and gains lifelink and indestructible until end of turn. (Damage dealt by that creature also causes its controller to gain that much life, and it can't be destroyed by damage or effects that say "destroy.")

Hooded Assassin

When Hooded Assassin enters, choose one —
• Put a +1/+1 counter on Hooded Assassin.
• Destroy target creature that was dealt damage this turn.

Lurking Deadeye

Flash
When Lurking Deadeye enters, destroy target creature that was dealt damage this turn.

Do or Die

Separate all creatures target player controls into two piles. Destroy all creatures in the pile of that player's choice. They can't be regenerated.

Subtle Strike

Choose one or both —
• Target creature gets -1/-1 until end of turn.
• Put a +1/+1 counter on target creature.

Vraska's Finisher

When Vraska's Finisher enters, destroy target creature or planeswalker an opponent controls that was dealt damage this turn.

Extinction

Destroy all creatures of the creature type of your choice.

King's Assassin

{T}: Destroy target tapped creature. Activate only during your turn, before attackers are declared.

Heartless Act

Choose one —
• Destroy target creature with no counters on it.
• Remove up to three counters from target creature.

Ruthless Ripper

Deathtouch
Morph—Reveal a black card in your hand. (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Ruthless Ripper is turned face up, target player loses 2 life.

Thorn of the Black Rose

Deathtouch
When Thorn of the Black Rose enters, you become the monarch.

Murder

Contagion

You may pay 1 life and exile a black card from your hand rather than pay this spell's mana cost.
Distribute two -2/-1 counters among one or two target creatures.

Big Game Hunter

When Big Game Hunter enters, destroy target creature with power 4 or greater. It can't be regenerated.
Madness {B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)