Each player loses a third of their life, then discards a third of the cards in their hand, then sacrifices a third of the creatures they control of their choice, then sacrifices a third of the lands they control of their choice. Round up each time.

Murder

Blighted Fen

{T}: Add {C}.
{4}{B}, {T}, Sacrifice this land: Target opponent sacrifices a creature of their choice.

Grave Pact

Whenever a creature you control dies, each other player sacrifices a creature of their choice.

Tainted Aether

Whenever a creature enters, its controller sacrifices a creature or land of their choice.

Rush of Dread

Spree (Choose one or more additional costs.)
+ {1} — Target opponent sacrifices half the creatures they control of their choice, rounded up.
+ {2} — Target opponent discards half the cards in their hand, rounded up.
+ {2} — Target opponent loses half their life, rounded up.

Fleshbag Marauder

When this creature enters, each player sacrifices a creature of their choice.

Tergrid's Lantern

{T}: Target player loses 3 life unless they sacrifice a nonland permanent of their choice or discard a card.
{3}{B}: Untap Tergrid's Lantern.

Tergrid, God of Fright

Menace
Whenever an opponent sacrifices a nontoken permanent or discards a permanent card, you may put that card from a graveyard onto the battlefield under your control.

Tergrid, God of Fright // Tergrid's Lantern

Plaguecrafter

When this creature enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.

Rankle, Master of Pranks

Flying, haste
Whenever Rankle deals combat damage to a player, choose any number —
• Each player discards a card.
• Each player loses 1 life and draws a card.
• Each player sacrifices a creature of their choice.

Necrogoyf

Necrogoyf's power is equal to the number of creature cards in all graveyards.
At the beginning of each player's upkeep, that player discards a card.
Madness {1}{B}{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.)

Diabolic Edict

Target player sacrifices a creature of their choice.

Stronghold Rats

Shadow (This creature can block or be blocked by only creatures with shadow.)
Whenever this creature deals combat damage to a player, each player discards a card.

Elvish Doomsayer

When this creature dies, each opponent discards a card.

Feast of Sanity

Whenever you discard a card, this enchantment deals 1 damage to any target and you gain 1 life.

Desolation

At the beginning of each end step, each player who tapped a land for mana this turn sacrifices a land of their choice. This enchantment deals 2 damage to each player who sacrificed a Plains this way.

Food

{2}, {T}, Sacrifice this token: You gain 3 life.

Skullslither Worm

When this creature enters, each opponent discards a card. For each opponent who can't, put two +1/+1 counters on this creature.

Abyssal Specter

Flying
Whenever this creature deals damage to a player, that player discards a card.

Temple of the Dead

(Transforms from Aclazotz, Deepest Betrayal.)
{T}: Add {B}.
{2}{B}, {T}: Transform this land. Activate only if a player has one or fewer cards in hand and only as a sorcery.

Aclazotz, Deepest Betrayal

Flying, lifelink
Whenever Aclazotz attacks, each opponent discards a card. For each opponent who can't, you draw a card.
Whenever an opponent discards a land card, create a 1/1 black Bat creature token with flying.
When Aclazotz dies, return it to the battlefield tapped and transformed under its owner's control.

Aclazotz, Deepest Betrayal // Temple of the Dead

Innocent Blood

Each player sacrifices a creature of their choice.

Witch's Cottage

({T}: Add {B}.)
This land enters tapped unless you control three or more other Swamps.
When this land enters untapped, you may put target creature card from your graveyard on top of your library.

Sangromancer

Flying
Whenever a creature an opponent controls dies, you may gain 3 life.
Whenever an opponent discards a card, you may gain 3 life.

Taste of Death

Each player sacrifices three creatures of their choice. You create three Food tokens. (They're artifacts with "{2}, {T}, Sacrifice this token: You gain 3 life.")

Sudden Edict

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Target player sacrifices a creature of their choice.

Barter in Blood

Each player sacrifices two creatures of their choice.

No Mercy

Whenever a creature deals damage to you, destroy it.

Awaken the Erstwhile

Each player discards all the cards in their hand, then creates that many 2/2 black Zombie creature tokens.

Tourach, Dread Cantor

Kicker {B}{B} (You may pay an additional {B}{B} as you cast this spell.)
Protection from white
Whenever an opponent discards a card, put a +1/+1 counter on Tourach.
When Tourach enters, if it was kicked, target opponent discards two cards at random.

Gray Merchant of Asphodel

When this creature enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Mindslicer

When this creature dies, each player discards their hand.

Archfiend of Depravity

Flying
At the beginning of each opponent's end step, that player chooses up to two creatures they control, then sacrifices the rest.

Fell Specter

Flying
When this creature enters, target opponent discards a card.
Whenever an opponent discards a card, that player loses 2 life.

Cerebral Confiscation

Choose one —
• Target opponent discards two cards.
• Target opponent reveals their hand. You choose a nonland card from it. That player discards that card.

Invoke Despair

Target opponent sacrifices a creature of their choice. If they can't, they lose 2 life and you draw a card. Then repeat this process for an enchantment and a planeswalker.

Miasmic Mummy

When this creature enters, each player discards a card.

Bojuka Bog

This land enters tapped.
When this land enters, exile target player's graveyard.
{T}: Add {B}.

Necrotic Hex

Each player sacrifices six creatures of their choice. You create six tapped 2/2 black Zombie creature tokens.

Sol Ring

Bird

Mind Rake

Target player discards two cards.
Overload {1}{B} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Demon's Disciple

When this creature enters, each player sacrifices a creature or planeswalker of their choice.

Oppression

Whenever a player casts a spell, that player discards a card.

Charcoal Diamond

This artifact enters tapped.
{T}: Add {B}.

Killing Wave

For each creature, its controller sacrifices it unless they pay X life.

Hypnotic Specter

Flying
Whenever this creature deals damage to an opponent, that player discards a card at random.

Black Market

Whenever a creature dies, put a charge counter on this enchantment.
At the beginning of your first main phase, add {B} for each charge counter on this enchantment.

Dark Ritual

Fraying Omnipotence

Each player loses half their life, then discards half the cards in their hand, then sacrifices half the creatures they control of their choice. Round up each time.

Zombie

Bone Miser

Whenever you discard a creature card, create a 2/2 black Zombie creature token.
Whenever you discard a land card, add {B}{B}.
Whenever you discard a noncreature, nonland card, draw a card.

Sheoldred's Edict

Choose one —
• Each opponent sacrifices a nontoken creature of their choice.
• Each opponent sacrifices a creature token of their choice.
• Each opponent sacrifices a planeswalker of their choice.

Death Cloud

Each player loses X life, discards X cards, sacrifices X creatures of their choice, then sacrifices X lands of their choice.

Bottomless Pit

At the beginning of each player's upkeep, that player discards a card at random.

Rankle's Prank

Choose one or more —
• Each player discards two cards.
• Each player loses 4 life.
• Each player sacrifices two creatures of their choice.

The Raven Man

At the beginning of each end step, if a player discarded a card this turn, create a 1/1 black Bird creature token with flying and "This token can't block."
{3}{B}, {T}: Each opponent discards a card. Activate only as a sorcery.

Braids, Arisen Nightmare

At the beginning of your end step, you may sacrifice an artifact, creature, enchantment, land, or planeswalker. If you do, each opponent may sacrifice a permanent of their choice that shares a card type with it. For each opponent who doesn't, that player loses 2 life and you draw a card.

Davriel, Rogue Shadowmage

At the beginning of each opponent's upkeep, if that player has one or fewer cards in hand, Davriel deals 2 damage to them.
−1: Target player discards a card.

Soul Shatter

Each opponent sacrifices a creature or planeswalker with the greatest mana value among creatures and planeswalkers they control.

Vicious Rumors

Vicious Rumors deals 1 damage to each opponent. Each opponent discards a card, then mills a card. You gain 1 life.

Cunning Lethemancer

At the beginning of your upkeep, each player discards a card.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Painful Quandary

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.

Blanket of Night

Each land is a Swamp in addition to its other land types.

Elderfang Disciple

When this creature enters, each opponent discards a card.

Megrim

Whenever an opponent discards a card, this enchantment deals 2 damage to that player.

Syphon Mind

Each other player discards a card. You draw a card for each card discarded this way.

Mire in Misery

Each opponent sacrifices a creature or enchantment of their choice.

Swamp

Waste Not

Whenever an opponent discards a creature card, create a 2/2 black Zombie creature token.
Whenever an opponent discards a land card, add {B}{B}.
Whenever an opponent discards a noncreature, nonland card, draw a card.

Dark Deal

Each player discards all the cards in their hand, then draws that many cards minus one.