Diregraf Captain

Deathtouch
Other Zombie creatures you control get +1/+1.
Whenever another Zombie you control dies, target opponent loses 1 life.

Zombie Master

Other Zombie creatures have swampwalk. (They can't be blocked as long as defending player controls a Swamp.)
Other Zombies have "{B}: Regenerate this permanent."

Undead Augur

Whenever this creature or another Zombie you control dies, you draw a card and you lose 1 life.

Gleaming Overseer

When this creature enters, amass Zombies 1. (Put a +1/+1 counter on an Army you control. It's also a Zombie. If you don't control an Army, create a 0/0 black Zombie Army creature token first.)
Zombie tokens you control have hexproof and menace.

Gravecrawler

This creature can't block.
You may cast this card from your graveyard as long as you control a Zombie.

Counterspell

Cryptbreaker

{1}{B}, {T}, Discard a card: Create a 2/2 black Zombie creature token.
Tap three untapped Zombies you control: You draw a card and you lose 1 life.

Rooftop Storm

You may pay {0} rather than pay the mana cost for Zombie creature spells you cast.

Diregraf Colossus

This creature enters with a +1/+1 counter on it for each Zombie card in your graveyard.
Whenever you cast a Zombie spell, create a tapped 2/2 black Zombie creature token.

Necroduality

Whenever a nontoken Zombie you control enters, create a token that's a copy of that creature.

Reassembling Skeleton

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

Reanimate

Put target creature card from a graveyard onto the battlefield under your control. You lose life equal to that card's mana value.

The Scarab God

At the beginning of your upkeep, each opponent loses X life and you scry X, where X is the number of Zombies you control.
{2}{U}{B}: Exile target creature card from a graveyard. Create a token that's a copy of it, except it's a 4/4 black Zombie.
When The Scarab God dies, return it to its owner's hand at the beginning of the next end step.