Demon of Death's Gate

You may pay 6 life and sacrifice three black creatures rather than pay this spell's mana cost.
Flying, trample

Athreos, God of Passage

Indestructible
As long as your devotion to white and black is less than seven, Athreos isn't a creature.
Whenever another creature you own dies, return it to your hand unless target opponent pays 3 life.

Attrition

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

Ghoulcaller Gisa

{B}, {T}, Sacrifice another creature: Create X 2/2 black Zombie creature tokens, where X is the sacrificed creature's power.

God-Eternal Bontu

Menace
When God-Eternal Bontu enters, sacrifice any number of other permanents, then draw that many cards.
When God-Eternal Bontu dies or is put into exile from the battlefield, you may put it into its owner's library third from the top.

Erebos, Bleak-Hearted

Indestructible
As long as your devotion to black is less than five, Erebos isn't a creature.
Whenever another creature you control dies, you may pay 2 life. If you do, draw a card.
{1}{B}, Sacrifice another creature: Target creature gets -2/-1 until end of turn.

Henrika, Infernal Seer

Flying, deathtouch, lifelink
{1}{B}{B}: Each creature you control with flying, deathtouch, and/or lifelink gets +1/+0 until end of turn.

Henrika Domnathi

Flying
At the beginning of combat on your turn, choose one that hasn't been chosen —
• Each player sacrifices a creature of their choice.
• You draw a card and you lose 1 life.
• Transform Henrika Domnathi.