Shepherd of Rot

{T}: Each player loses 1 life for each Zombie on the battlefield.

Swamp

Vengeful Dead

Whenever Vengeful Dead or another Zombie dies, each opponent loses 1 life.

Festering Goblin

When Festering Goblin dies, target creature gets -1/-1 until end of turn.

Putrid Imp

Discard a card: Putrid Imp gains flying until end of turn.
Threshold — As long as seven or more cards are in your graveyard, Putrid Imp gets +1/+1 and can't block.

Carrion Feeder

Carrion Feeder can't block.
Sacrifice a creature: Put a +1/+1 counter on Carrion Feeder.

Carnophage

At the beginning of your upkeep, tap Carnophage unless you pay 1 life.

Diabolic Edict

Target player sacrifices a creature of their choice.

Vendetta

Destroy target nonblack creature. It can't be regenerated. You lose life equal to that creature's toughness.

Gempalm Polluter

Cycling {B}{B} ({B}{B}, Discard this card: Draw a card.)
When you cycle Gempalm Polluter, you may have target player lose life equal to the number of Zombies on the battlefield.

Dark Ritual

Chainer's Edict

Target player sacrifices a creature of their choice.
Flashback {5}{B}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)