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.

Living Death

Each player exiles all creature cards from their graveyard, then sacrifices all creatures they control, then puts all cards they exiled this way onto the battlefield.

Magus of the Bridge

Whenever a nontoken creature is put into your graveyard from the battlefield, create a 2/2 black Zombie creature token.
When a creature is put into an opponent's graveyard from the battlefield, exile this creature.

Demonic Tutor

Search your library for a card, put that card into your hand, then shuffle.

Lifeline

Whenever a creature dies, if another creature is on the battlefield, return the first card to the battlefield under its owner's control at the beginning of the next end step.

Jet Medallion

Black spells you cast cost {1} less to cast.

Gisa, Glorious Resurrector

If a creature an opponent controls would die, exile it instead.
At the beginning of your upkeep, put all creature cards exiled with Gisa onto the battlefield under your control. They gain decayed. (A creature with decayed can't block. When it attacks, sacrifice it at end of combat.)

Homeward Path

{T}: Add {C}.
{T}: Each player gains control of all creatures they own.

Carrion Feeder

This creature can't block.
Sacrifice a creature: Put a +1/+1 counter on this creature.

Hellfire

Destroy all nonblack creatures. Hellfire deals X plus 3 damage to you, where X is the number of creatures that died this way.

Attrition

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

Accursed Marauder

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

Toxic Deluge

As an additional cost to cast this spell, pay X life.
All creatures get -X/-X until end of turn.

Bridge from Below

Whenever a nontoken creature is put into your graveyard from the battlefield, if this card is in your graveyard, create a 2/2 black Zombie creature token.
When a creature is put into an opponent's graveyard from the battlefield, if this card is in your graveyard, exile this card.

Grave Pact

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

Smallpox

Each player loses 1 life, discards a card, sacrifices a creature of their choice, then sacrifices a land of their choice.

Dark Ritual

Avatar of Woe

If there are ten or more creature cards total in all graveyards, this spell costs {6} less to cast.
Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
{T}: Destroy target creature. It can't be regenerated.

Flare of Malice

You may sacrifice a nontoken black creature rather than pay this spell's mana cost.
Each opponent sacrifices a creature or planeswalker with the greatest mana value among creatures and planeswalkers they control.

Viscera Seer

Sacrifice a creature: Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Royal Assassin

Sign in Blood

Target player draws two cards and loses 2 life.

Icy Manipulator

{1}, {T}: Tap target artifact, creature, or land.

Reanimate

Put target creature card from a graveyard onto the battlefield under your control. You lose life equal to its mana value.

Keeper of the Dead

{B}, {T}: Choose target opponent who has at least two fewer creature cards in their graveyard than you do as you activate this ability. Destroy target nonblack creature that player controls.

Vampiric Tutor

Search your library for a card, then shuffle and put that card on top. You lose 2 life.