Clutch of Undeath

Enchant creature
Enchanted creature gets +3/+3 as long as it's a Zombie. Otherwise, it gets -3/-3.

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.)

Gavony Unhallowed

Whenever another creature you control dies, put a +1/+1 counter on Gavony Unhallowed.

Ghoulraiser

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

Undead Servant

When Undead Servant enters, create a 2/2 black Zombie creature token for each card named Undead Servant in your graveyard.

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.)

Gray Merchant of Asphodel

When Gray Merchant of Asphodel enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Shamble Back

Exile target creature card from a graveyard. Create a 2/2 black Zombie creature token. You gain 2 life.

Rank Officer

When Rank Officer enters, you may discard a card. If you do, create a 2/2 black Zombie creature token.
{1}{B}, {T}, Exile a creature card from your graveyard: Each opponent loses 2 life.

Fleshbag Marauder

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

Gempalm Polluter

Cycling {B}{B} ({B}{B}, Discard this card: Draw a card.)
When you cycle Gempalm Polluter, you may have target player lose life equal to the number of Zombies on the battlefield.