Headless Rider

Whenever Headless Rider or another nontoken Zombie you control dies, create a 2/2 black Zombie creature token.

Diregraf Colossus

Diregraf Colossus 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.

Endless Ranks of the Dead

At the beginning of your upkeep, create X 2/2 black Zombie creature tokens, where X is half the number of Zombies you control, rounded down.

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.

Tainted Adversary

Deathtouch
When Tainted Adversary enters, you may pay {2}{B} any number of times. When you pay this cost one or more times, put that many +1/+1 counters on Tainted Adversary, then create twice that many 2/2 black Zombie creature tokens with decayed. (A creature with decayed can't block. When it attacks, sacrifice it at end of combat.)

Crawl from the Cellar

Return target creature card from your graveyard to your hand. Put a +1/+1 counter on up to one target Zombie you control.
Flashback {3}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Undead Augur

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

Graveborn Muse

At the beginning of your upkeep, you draw X cards and you lose X life, where X is the number of Zombies you control.

Gravecrawler

Gravecrawler can't block.
You may cast Gravecrawler from your graveyard as long as you control a Zombie.

Call to the Grave

At the beginning of each player's upkeep, that player sacrifices a non-Zombie creature.
At the beginning of the end step, if no creatures are on the battlefield, sacrifice Call to the Grave.

Swamp

Death Baron

Skeletons you control and other Zombies you control get +1/+1 and have deathtouch.

Champion of the Perished

Whenever another Zombie you control enters, put a +1/+1 counter on Champion of the Perished.