Mausoleum Secrets

Undergrowth — Search your library for a black card with mana value less than or equal to the number of creature cards in your graveyard, reveal it, put it into your hand, then shuffle.

Wilhelt, the Rotcleaver

Whenever another Zombie you control dies, if it didn't have decayed, create a 2/2 black Zombie creature token with decayed. (It can't block. When it attacks, sacrifice it at end of combat.)
At the beginning of your end step, you may sacrifice a Zombie. If you do, draw a card.

Carnival of Souls

Whenever a creature enters, you lose 1 life and add {B}.

Aura Flux

Other enchantments have "At the beginning of your upkeep, sacrifice this enchantment unless you pay {2}."

Diplomatic Immunity

Enchant creature
Shroud (A permanent with shroud can't be the target of spells or abilities.)
Enchanted creature has shroud.

Rotting Regisaur

At the beginning of your upkeep, discard a card.

Ravenform

Exile target artifact or creature. Its controller creates a 1/1 blue Bird creature token with flying.
Foretell {U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Bontu's Monument

Black creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.

Morbid Opportunist

Whenever one or more other creatures die, draw a card. This ability triggers only once each turn.

Ormendahl, Profane Prince

Westvale Abbey

{T}: Add {C}.
{5}, {T}, Pay 1 life: Create a 1/1 white and black Human Cleric creature token.
{5}, {T}, Sacrifice five creatures: Transform Westvale Abbey, then untap it.

Westvale Abbey // Ormendahl, Profane Prince

Songs of the Damned

Add {B} for each creature card in your graveyard.

Attrition

{B}, Sacrifice a creature: Destroy target nonblack creature.

Attunement

Return Attunement to its owner's hand: Draw three cards, then discard four cards.

Oath of Ghouls

At the beginning of each player's upkeep, that player chooses target player whose graveyard has fewer creature cards in it than their graveyard does and is their opponent. The first player may return a creature card from their graveyard to their hand.

The Meathook Massacre

When The Meathook Massacre enters, each creature gets -X/-X until end of turn.
Whenever a creature you control dies, each opponent loses 1 life.
Whenever a creature an opponent controls dies, you gain 1 life.