Gravecrawler

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

Swamp

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

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

Whenever Headless Rider or another nontoken Zombie you control dies, create a 2/2 black Zombie creature token.

{1}{B}, {T}, Discard a card: Create a 2/2 black Zombie creature token.
Tap three untapped Zombies you control: You draw a card and you lose 1 life.

When Miasmic Mummy enters, each player discards a card.

Flying
You may cast Scourge of Nel Toth from your graveyard by paying {B}{B} and sacrificing two creatures rather than paying its mana cost.

Return up to two target creature cards from your graveyard to your hand, then discard a card.

Destroy target creature. You lose 2 life.

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