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.

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.

Leechridden Swamp

({T}: Add {B}.)
Leechridden Swamp enters tapped.
{B}, {T}: Each opponent loses 1 life. Activate only if you control two or more black permanents.

Skeletal Grimace

Enchant creature
Enchanted creature gets +1/+1 and has "{B}: Regenerate this creature."

Dead Weight

Enchant creature
Enchanted creature gets -2/-2.

Markov Patrician

Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Relentless Dead

Menace (This creature can't be blocked except by two or more creatures.)
When Relentless Dead dies, you may pay {B}. If you do, return it to its owner's hand.
When Relentless Dead dies, you may pay {X}. If you do, return another target Zombie creature card with mana value X from your graveyard to the battlefield.

Manor Skeleton

Ghoulcaller's Bell

Typhoid Rats

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)

Disciple of Griselbrand

{1}, Sacrifice a creature: You gain life equal to the sacrificed creature's toughness.

Rottenheart Ghoul

When Rottenheart Ghoul dies, target player discards a card.

Diregraf Ghoul

Pale Rider of Trostad

Skulk (This creature can't be blocked by creatures with greater power.)
When Pale Rider of Trostad enters, discard a card.

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.

Swamp

Tribute to Hunger

Target opponent sacrifices a creature. You gain life equal to that creature's toughness.

Altar's Reap

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Ghoulraiser

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