Skeleton Crew

Each other creature you control that's a Skeleton or Pirate gets +1/+1.
Whenever one or more creature cards leave your graveyard, create a 2/2 black Skeleton Pirate creature token. (This ability triggers only from the battlefield.)
{5}{B}: Return Skeleton Crew from your graveyard to the battlefield tapped.

Persistent Specimen

{2}{B}: Return Persistent Specimen from your graveyard to the battlefield tapped.

Dark Ritual

Valgavoth, Terror Eater

Flying, lifelink
Ward—Sacrifice three nonland permanents.
If a card you didn't control would be put into an opponent's graveyard from anywhere, exile it instead.
During your turn, you may play cards exiled with Valgavoth. If you cast a spell this way, pay life equal to its mana value rather than pay its mana cost.

Magus of the Coffers

{2}, {T}: Add {B} for each Swamp you control.

Reassembling Skeleton

{1}{B}: Return Reassembling Skeleton from your graveyard to the battlefield tapped.

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.

Death Baron

Skeletons you control and other Zombies you control get +1/+1 and have deathtouch.

Headless Rider

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

Crypt Ghast

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Whenever you tap a Swamp for mana, add an additional {B}.

Cabal Coffers

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.)

Sanitarium Skeleton

{2}{B}: Return Sanitarium Skeleton from your graveyard to your hand.

Acererak the Archlich

When Acererak the Archlich enters, if you haven't completed Tomb of Annihilation, return Acererak the Archlich to its owner's hand and venture into the dungeon.
Whenever Acererak the Archlich attacks, for each opponent, you create a 2/2 black Zombie creature token unless that player sacrifices a creature.