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.

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.)

Swamp

Gutter Skulk

Zombie Apocalypse

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

Havengul Lich

{1}: You may cast target creature card in a graveyard this turn. When you cast it this turn, Havengul Lich gains all activated abilities of that card until end of turn.

Island

Two-Headed Zombie

Menace (This creature can't be blocked except by two or more creatures.)

Diregraf Ghoul

Corpse Blockade

Defender
Sacrifice another creature: Corpse Blockade gains deathtouch until end of turn.

Dregscape Zombie

Unearth {B} ({B}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Dread Wanderer

Dread Wanderer enters tapped.
{2}{B}: Return Dread Wanderer from your graveyard to the battlefield. Activate only as a sorcery and only if you have one or fewer cards in hand.

Diregraf Captain

Deathtouch
Other Zombie creatures you control get +1/+1.
Whenever another Zombie you control dies, target opponent loses 1 life.

Abattoir Ghoul

First strike
Whenever a creature dealt damage by Abattoir Ghoul this turn dies, you gain life equal to that creature's toughness.