Voracious Null

{1}{B}, Sacrifice another creature: Put two +1/+1 counters on Voracious Null. Activate only as a sorcery.

Ghouls' Night Out

For each player, choose a creature card in that player's graveyard. Put those cards onto the battlefield under your control. They're black Zombies in addition to their other colors and types and they gain decayed. (A creature with decayed can't block. When it attacks, sacrifice it at end of combat.)

Innocent Blood

Each player sacrifices a creature of their choice.

Ghoulcaller's Chant

Choose one —
• Return target creature card from your graveyard to your hand.
• Return two target Zombie cards from your graveyard to your hand.

Noxious Ghoul

Whenever Noxious Ghoul or another Zombie enters, all non-Zombie creatures get -1/-1 until end of turn.

Butcher Ghoul

Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Tragic Slip

Target creature gets -1/-1 until end of turn.
Morbid — That creature gets -13/-13 until end of turn instead if a creature died this turn.

Abattoir Ghoul

First strike
Whenever a creature dealt damage by Abattoir Ghoul this turn dies, you gain life equal to that creature's toughness.

Gavony Unhallowed

Whenever another creature you control dies, put a +1/+1 counter on Gavony Unhallowed.

Diregraf Ghoul

Ghoulraiser

When Ghoulraiser enters, return a Zombie card at random from your graveyard to your hand.

Liliana's Mastery

Zombies you control get +1/+1.
When Liliana's Mastery enters, create two 2/2 black Zombie creature tokens.