Have

Stitcher's Supplier

When Stitcher's Supplier enters or dies, mill three cards. (Put the top three cards of your library into your graveyard.)

Champion of the Perished

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

Gravecrawler

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

Oversold Cemetery

At the beginning of your upkeep, if you have four or more creature cards in your graveyard, you may return target creature card from your graveyard to your hand.

Unearth

Return target creature card with mana value 3 or less from your graveyard to the battlefield.
Cycling {2} ({2}, Discard this card: Draw a card.)

Go for the Throat

Swift End

Destroy target creature or planeswalker. You lose 2 life. (Then exile this card. You may cast the creature later from exile.)

Murderous Rider

Lifelink
When Murderous Rider dies, put it on the bottom of its owner's library.

Murderous Rider // Swift End

Mortuary Mire

Mortuary Mire enters tapped.
When Mortuary Mire enters, you may put target creature card from your graveyard on top of your library.
{T}: Add {B}.

Zombie Apocalypse

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

Mire Triton

Deathtouch
When Mire Triton enters, mill two cards and you gain 2 life. (To mill a card, put the top card of your library into your graveyard.)

Victimize

Choose two target creature cards in your graveyard. Sacrifice a creature. If you do, return the chosen cards to the battlefield tapped.

Grave Pact

Whenever a creature you control dies, each other player sacrifices a creature of their choice.

Getting

Undead Butler

When Undead Butler enters, mill three cards. (Put the top three cards of your library into your graveyard.)
When Undead Butler dies, you may exile it. When you do, return target creature card from your graveyard to your hand.

Bone Shards

As an additional cost to cast this spell, sacrifice a creature or discard a card.
Destroy target creature or planeswalker.

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.

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.

Deathmark

Tainted Remedy

If an opponent would gain life, that player loses that much life instead.

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.)

Terror Tide

Fathomless descent — All creatures get -X/-X until end of turn, where X is the number of permanent cards in your graveyard.