Festercreep

Festercreep enters with a +1/+1 counter on it.
{1}{B}, Remove a +1/+1 counter from Festercreep: All other creatures get -1/-1 until end of turn.

Bog Elemental

Protection from white
At the beginning of your upkeep, sacrifice Bog Elemental unless you sacrifice a land.

Mournwhelk

When Mournwhelk enters, target player discards two cards.
Evoke {3}{B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Maze Abomination

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Multicolored creatures you control have deathtouch.

Shriekmaw

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
When Shriekmaw enters, destroy target nonartifact, nonblack creature.
Evoke {1}{B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Stenchskipper

Flying
At the beginning of the end step, if you control no Goblins, sacrifice Stenchskipper.

Umbra Stalker

Chroma — Umbra Stalker's power and toughness are each equal to the number of black mana symbols in the mana costs of cards in your graveyard.

Corrosive Mentor

Black creatures you control have wither. (They deal damage to creatures in the form of -1/-1 counters.)

Cinderhaze Wretch

{T}: Target player discards a card. Activate only during your turn.
Put a -1/-1 counter on Cinderhaze Wretch: Untap Cinderhaze Wretch.

Ashenmoor Cohort

Ashenmoor Cohort gets +1/+1 as long as you control another black creature.

Tar Fiend

Devour 2 (As this enters, you may sacrifice any number of creatures. This creature enters with twice that many +1/+1 counters on it.)
When Tar Fiend enters, target player discards a card for each creature it devoured.

Geyserfield Stalker

Menace (This creature can't be blocked except by two or more creatures.)
Landfall — Whenever a land you control enters, Geyserfield Stalker gets +2/+2 until end of turn.

Grief

Menace
When Grief enters, target opponent reveals their hand. You choose a nonland card from it. That player discards that card.
Evoke—Exile a black card from your hand.

Smolder Initiate

Whenever a player casts a black spell, you may pay {1}. If you do, target player loses 1 life.

Necroskitter

Wither (This deals damage to creatures in the form of -1/-1 counters.)
Whenever a creature an opponent controls with a -1/-1 counter on it dies, you may return that card to the battlefield under your control.

Desecration Elemental

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Whenever a player casts a spell, sacrifice a creature.

Cavalier of Night

Lifelink
When Cavalier of Night enters, you may sacrifice another creature. When you do, destroy target creature an opponent controls.
When Cavalier of Night dies, return target creature card with mana value 3 or less from your graveyard to the battlefield.

Sickle Ripper

Wither (This deals damage to creatures in the form of -1/-1 counters.)

Ashling, the Extinguisher

Whenever Ashling, the Extinguisher deals combat damage to a player, choose target creature that player controls. The player sacrifices that creature.

Crowd of Cinders

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Crowd of Cinders's power and toughness are each equal to the number of black permanents you control.

Soul Snuffers

When Soul Snuffers enters, put a -1/-1 counter on each creature.

Dread

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Whenever a creature deals damage to you, destroy it.
When Dread is put into a graveyard from anywhere, shuffle it into its owner's library.

Smog Elemental

Flying
Creatures with flying your opponents control get -1/-1.

Insidious Mist

Hexproof, indestructible
Insidious Mist can't block and can't be blocked.
Whenever Insidious Mist attacks and isn't blocked, you may pay {2}{B}. If you do, transform it.

Elusive Tormentor

{1}, Discard a card: Transform Elusive Tormentor.

Elusive Tormentor // Insidious Mist

Smoldering Butcher

Night Incarnate

Deathtouch
When Night Incarnate leaves the battlefield, all creatures get -3/-3 until end of turn.
Evoke {3}{B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Rotted Hulk

Cinderbones

Wither (This deals damage to creatures in the form of -1/-1 counters.)
{1}{B}: Regenerate Cinderbones.

Baleful Force

At the beginning of each upkeep, you draw a card and you lose 1 life.

Offalsnout

Flash
When Offalsnout leaves the battlefield, exile target card from a graveyard.
Evoke {B} (You may cast this spell for its evoke cost. If you do, it's sacrificed when it enters.)

Nyxathid

As Nyxathid enters, choose an opponent.
Nyxathid gets -1/-1 for each card in the chosen player's hand.