Contamination

At the beginning of your upkeep, sacrifice Contamination unless you sacrifice a creature.
If a land is tapped for mana, it produces {B} instead of any other type and amount.

Merciless Executioner

When Merciless Executioner enters the battlefield, each player sacrifices a creature.

Voltaic Key

Fleshbag Marauder

When Fleshbag Marauder enters the battlefield, each player sacrifices a creature.

Bojuka Bog

Bojuka Bog enters the battlefield tapped.
When Bojuka Bog enters the battlefield, exile target player's graveyard.
{T}: Add {B}.

Ob Nixilis, Unshackled

Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis, Unshackled.

Entomb

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

Temporal Extortion

When you cast this spell, any player may pay half their life, rounded up. If a player does, counter Temporal Extortion.
Take an extra turn after this one.

Leyline of the Void

If Leyline of the Void is in your opening hand, you may begin the game with it on the battlefield.
If a card would be put into an opponent's graveyard from anywhere, exile it instead.

Sheoldred, Whispering One

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
At the beginning of your upkeep, return target creature card from your graveyard to the battlefield.
At the beginning of each opponent's upkeep, that player sacrifices a creature.

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.

Sidisi, Undead Vizier

Deathtouch
Exploit (When this creature enters the battlefield, you may sacrifice a creature.)
When Sidisi, Undead Vizier exploits a creature, you may search your library for a card, put it into your hand, then shuffle.

Vile Entomber

Deathtouch
When Vile Entomber enters the battlefield, search your library for a card, put that card into your graveyard, then shuffle.