Unbreathing Horde

Unbreathing Horde enters with a +1/+1 counter on it for each other Zombie you control and each Zombie card in your graveyard.
If Unbreathing Horde would be dealt damage, prevent that damage and remove a +1/+1 counter from it.

Quest for the Gravelord

Whenever a creature dies, you may put a quest counter on Quest for the Gravelord.
Remove three quest counters from Quest for the Gravelord and sacrifice it: Create a 5/5 black Zombie Giant creature token.

Those Who Serve

Gurmag Angler

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)

Gisa's Bidding

Create two 2/2 black Zombie creature tokens.
Madness {2}{B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Plague Wind

Destroy all creatures you don't control. They can't be regenerated.

Death Baron

Skeletons you control and other Zombies you control get +1/+1 and have deathtouch. (Any amount of damage they deal to a creature is enough to destroy it.)

Dutiful Servants

Northern Paladin

{W}{W}, {T}: Destroy target black permanent.

Zombie Apocalypse

Return all Zombie creature cards from your graveyard to the battlefield tapped, then destroy all Humans.

Syphon Flesh

Each other player sacrifices a creature. You create a 2/2 black Zombie creature token for each creature sacrificed this way.

Armillary Sphere

{2}, {T}, Sacrifice Armillary Sphere: Search your library for up to two basic land cards, reveal them, put them into your hand, then shuffle.

Extremely Slow Zombie

Last strike (This creature deals combat damage after creatures without last strike.)

Bad Moon

Army of the Damned

Create thirteen tapped 2/2 black Zombie creature tokens.
Flashback {7}{B}{B}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Scathe Zombies

Damnation

Destroy all creatures. They can't be regenerated.

Liliana's Reaver

Deathtouch
Whenever Liliana's Reaver deals combat damage to a player, that player discards a card and you create a tapped 2/2 black Zombie creature token.

Vengeful Dead

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

Angel of Glory's Rise

Flying
When Angel of Glory's Rise enters, exile all Zombies, then return all Human creature cards from your graveyard to the battlefield.

Infectious Horror

Whenever Infectious Horror attacks, each opponent loses 2 life.

Moan of the Unhallowed

Create two 2/2 black Zombie creature tokens.
Flashback {5}{B}{B} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Howling Golem

Whenever Howling Golem attacks or blocks, each player draws a card.

Grave Titan

Deathtouch
Whenever Grave Titan enters or attacks, create two 2/2 black Zombie creature tokens.

Stir the Sands

Create three 2/2 black Zombie creature tokens.
Cycling {3}{B} ({3}{B}, Discard this card: Draw a card.)
When you cycle Stir the Sands, create a 2/2 black Zombie creature token.

Undead Warchief

Zombie spells you cast cost {1} less to cast.
Zombie creatures you control get +2/+1.

Call to the Grave

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

Dread Slaver

Whenever a creature dealt damage by Dread Slaver this turn dies, return it to the battlefield under your control. That creature is a black Zombie in addition to its other colors and types.

Fleshbag Marauder

When Fleshbag Marauder enters, each player sacrifices a creature of their choice.