Have

Nightshade Seer

{2}{B}, {T}: Reveal any number of black cards in your hand. Target creature gets -X/-X until end of turn, where X is the number of cards revealed this way.

Dark Ritual

Polluted Mire

This land enters tapped.
{T}: Add {B}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Body Snatcher

When this creature enters, exile it unless you discard a creature card.
When this creature dies, exile it and return target creature card from your graveyard to the battlefield.

Sanguine Guard

First strike
{1}{B}: Regenerate this creature.

Slinking Skirge

Flying
{2}, Sacrifice this creature: Draw a card.

Disease Carriers

When this creature dies, target creature gets -2/-2 until end of turn.

Dying Wail

Enchant creature
When enchanted creature dies, target player discards two cards.

Ostracize

Target opponent reveals their hand. You choose a creature card from it. That player discards that card.

Scent of Nightshade

Reveal any number of black cards in your hand. Target creature gets -X/-X until end of turn, where X is the number of cards revealed this way.

Mantis Engine

{2}: This creature gains flying until end of turn. (It can't be blocked except by creatures with flying or reach.)
{2}: This creature gains first strike until end of turn. (It deals combat damage before creatures without first strike.)

Engineered Plague

As this enchantment enters, choose a creature type.
All creatures of the chosen type get -1/-1.

Swamp

Bone Shredder

Flying
Echo {2}{B} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When this creature enters, destroy target nonartifact, nonblack creature.

Looming Shade

{B}: This creature gets +1/+1 until end of turn.

Festering Wound

Enchant creature
At the beginning of your upkeep, you may put an infection counter on this Aura.
At the beginning of the upkeep of enchanted creature's controller, this Aura deals X damage to that player, where X is the number of infection counters on this Aura.

Despondency

Enchant creature
Enchanted creature gets -2/-0.
When this Aura is put into a graveyard from the battlefield, return it to its owner's hand.

Ravenous Rats

When this creature enters, target opponent discards a card.

Attrition

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

Order of Yawgmoth

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Whenever this creature deals damage to a player, that player discards a card.

Soul Feast

Target player loses 4 life and you gain 4 life.

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Plague Dogs

When this creature dies, all creatures get -1/-1 until end of turn.
{2}, Sacrifice this creature: Draw a card.

Spawning Pool

This land enters tapped.
{T}: Add {B}.
{1}{B}: This land becomes a 1/1 black Skeleton creature with "{B}: Regenerate this creature" until end of turn. It's still a land. (If it regenerates, the next time it would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Sicken

Enchant creature
Enchanted creature gets -1/-1.
Cycling {2} ({2}, Discard this card: Draw a card.)

Eradicate

Exile target nonblack creature. Search its controller's graveyard, hand, and library for all cards with the same name as that creature and exile them. Then that player shuffles.

Squirming Mass

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)