Grave Pact

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

Reassembling Skeleton

{1}{B}: Return this card from your graveyard to the battlefield tapped.

Dina, Soul Steeper

Whenever you gain life, each opponent loses 1 life.
{1}, Sacrifice another creature: Dina gets +X/+0 until end of turn, where X is the sacrificed creature's power.

Savra, Queen of the Golgari

Whenever you sacrifice a black creature, you may pay 2 life. If you do, each other player sacrifices a creature of their choice.
Whenever you sacrifice a green creature, you may gain 2 life.

Ashnod's Altar

Erebos, God of the Dead

Indestructible
As long as your devotion to black is less than five, Erebos isn't a creature. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)
Your opponents can't gain life.
{1}{B}, Pay 2 life: Draw a card.

Tainted Aether

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

Grim Feast

At the beginning of your upkeep, this enchantment deals 1 damage to you.
Whenever a creature is put into an opponent's graveyard from the battlefield, you gain life equal to its toughness.

Blood Artist

Whenever this creature or another creature dies, target player loses 1 life and you gain 1 life.

Creakwood Liege

Other black creatures you control get +1/+1.
Other green creatures you control get +1/+1.
At the beginning of your upkeep, you may create a 1/1 black and green Worm creature token.