Vile Requiem

At the beginning of your upkeep, you may put a verse counter on Vile Requiem.
{1}{B}, Sacrifice Vile Requiem: Destroy up to X target nonblack creatures, where X is the number of verse counters on Vile Requiem. They can't be regenerated.

Splatter Goblin

When Splatter Goblin dies, target creature an opponent controls gets -1/-1 until end of turn.

Yargle, Glutton of Urborg

Songs of the Damned

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

Scorching Dragonfire

Scorching Dragonfire deals 3 damage to target creature or planeswalker. If that creature or planeswalker would die this turn, exile it instead.

Geth, Lord of the Vault

Intimidate (This creature can't be blocked except by artifact creatures and/or creatures that share a color with it.)
{X}{B}: Put target artifact or creature card with mana value X from an opponent's graveyard onto the battlefield under your control tapped. Then that player mills X cards.

Knight of Dusk's Shadow

Menace (This creature can't be blocked except by two or more creatures.)
Your opponents can't gain life.
{1}{B}: Knight of Dusk's Shadow gets +1/+1 until end of turn.

Virus Beetle

When Virus Beetle enters, each opponent discards a card.

Tyrannical Pitlord

Flying, trample
As Tyrannical Pitlord enters, choose another creature you control.
The chosen creature gets +3/+3 and has flying.
When Tyrannical Pitlord leaves the battlefield, sacrifice the chosen creature.

Davriel, Rogue Shadowmage

At the beginning of each opponent's upkeep, if that player has one or fewer cards in hand, Davriel, Rogue Shadowmage deals 2 damage to them.
−1: Target player discards a card.

Stingerback Terror

Flying, trample
Stingerback Terror gets -1/-1 for each card in your hand.
Plot {2}{R} (You may pay {2}{R} and exile this card from your hand. Cast it as a sorcery on a later turn without paying its mana cost. Plot only as a sorcery.)

Ob Nixilis of the Black Oath

+2: Each opponent loses 1 life. You gain life equal to the life lost this way.
−2: Create a 5/5 black Demon creature token with flying. You lose 2 life.
−8: You get an emblem with "{1}{B}, Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power."
Ob Nixilis of the Black Oath can be your commander.

Grasp of Darkness

Target creature gets -4/-4 until end of turn.

Battle-Rage Blessing

Target creature gains deathtouch and indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Cut Down

Destroy target creature with total power and toughness 5 or less.

Swamp

Gore-House Chainwalker

Unleash (You may have this creature enter with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)

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.)

Judith, the Scourge Diva

Other creatures you control get +1/+0.
Whenever a nontoken creature you control dies, Judith, the Scourge Diva deals 1 damage to any target.

Mountain

Rampaging Spiketail

When Rampaging Spiketail enters, target creature you control gets +2/+0 and gains indestructible until end of turn.
Swampcycling {2} ({2}, Discard this card: Search your library for a Swamp card, reveal it, put it into your hand, then shuffle.)

Torgaar, Famine Incarnate

As an additional cost to cast this spell, you may sacrifice any number of creatures. This spell costs {2} less to cast for each creature sacrificed this way.
When Torgaar, Famine Incarnate enters, up to one target player's life total becomes half their starting life total, rounded down.

Scion of Darkness

Trample
Whenever Scion of Darkness deals combat damage to a player, you may put target creature card from that player's graveyard onto the battlefield under your control.
Cycling {3} ({3}, Discard this card: Draw a card.)

Dread Return

Return target creature card from your graveyard to the battlefield.
Flashback—Sacrifice three creatures. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Gurgling Anointer

Flying
Whenever you draw your second card each turn, put a +1/+1 counter on Gurgling Anointer.
When Gurgling Anointer dies, return another target creature card with mana value less than or equal to Gurgling Anointer's power from your graveyard to the battlefield.

Lukka, Coppercoat Outcast

+1: Exile the top three cards of your library. Creature cards exiled this way gain "You may cast this card from exile as long as you control a Lukka planeswalker."
−2: Exile target creature you control, then reveal cards from the top of your library until you reveal a creature card with higher mana value. Put that card onto the battlefield and the rest on the bottom of your library in a random order.
−7: Each creature you control deals damage equal to its power to each opponent.

Carrion Grub

Carrion Grub gets +X/+0, where X is the greatest power among creature cards in your graveyard.
When Carrion Grub enters, mill four cards. (Put the top four cards of your library into your graveyard.)

Bloodfray Giant

Trample
Unleash (You may have this creature enter with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)

Ob Nixilis Reignited

+1: You draw a card and you lose 1 life.
−3: Destroy target creature.
−8: Target opponent gets an emblem with "Whenever a player draws a card, you lose 2 life."