Havengul Skaab

Whenever Havengul Skaab attacks, return another creature you control to its owner's hand.

Sludge Monster

Whenever Sludge Monster enters or attacks, put a slime counter on up to one other target creature.
Non-Horror creatures with slime counters on them lose all abilities and have base power and toughness 2/2.

Laboratory Drudge

At the beginning of each end step, draw a card if you've cast a spell from a graveyard or activated an ability of a card in a graveyard this turn.

Umbris, Fear Manifest

Umbris, Fear Manifest gets +1/+1 for each card your opponents own in exile.
Whenever Umbris or another Nightmare or Horror you control enters, target opponent exiles cards from the top of their library until they exile a land card.

Stitchwing Skaab

Flying
{1}{U}, Discard two cards: Return Stitchwing Skaab from your graveyard to the battlefield tapped.

Cleaver Skaab

{3}, {T}, Sacrifice another Zombie: Create two tokens that are copies of the sacrificed creature.

Patchwork Crawler

{2}{U}: Exile target creature card from your graveyard and put a +1/+1 counter on Patchwork Crawler.
Patchwork Crawler has all activated abilities of all creature cards exiled with it.

Tasha's Hideous Laughter

Each opponent exiles cards from the top of their library until that player has exiled cards with total mana value 20 or more.

Laboratory Brute

When Laboratory Brute enters, mill four cards.

Geralf's Masterpiece

Flying
Geralf's Masterpiece gets -1/-1 for each card in your hand.
{3}{U}, Discard three cards: Return Geralf's Masterpiece from your graveyard to the battlefield tapped.

Stitched Mangler

Stitched Mangler enters tapped.
When Stitched Mangler enters, tap target creature an opponent controls. That creature doesn't untap during its controller's next untap step.

Geralf's Mindcrusher

When Geralf's Mindcrusher enters, target player mills five cards.
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Skaab Ruinator

As an additional cost to cast this spell, exile three creature cards from your graveyard.
Flying
You may cast Skaab Ruinator from your graveyard.

Lamplighter of Selhoff

When Lamplighter of Selhoff enters, if you control another Zombie, you may draw a card. If you do, discard a card.

Ravenous Rotbelly

When Ravenous Rotbelly enters, you may sacrifice up to three Zombies. When you sacrifice one or more Zombies this way, each opponent sacrifices that many creatures of their choice.

Spoils of Blood

Create an X/X black Horror creature token, where X is the number of creatures that died this turn.

Hordewing Skaab

Flying
Other Zombies you control have flying.
Whenever one or more Zombies you control deal combat damage to one or more of your opponents, you may draw cards equal to the number of opponents dealt damage this way. If you do, discard that many cards.

Makeshift Mauler

As an additional cost to cast this spell, exile a creature card from your graveyard.

Drownyard Amalgam

When Drownyard Amalgam enters, target player mills three cards. (They put the top three cards of their library into their graveyard.)
{2}{U}: Drownyard Amalgam can't be blocked this turn.

Advanced Stitchwing

Flying
{2}{U}, Discard two cards: Return Advanced Stitchwing from your graveyard to the battlefield tapped.

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.