Demon of Loathing

Flying, trample
Whenever this creature deals combat damage to a player, that player sacrifices a creature of their choice.

Chainer, Dementia Master

All Nightmares get +1/+1.
{B}{B}{B}, Pay 3 life: Put target creature card from a graveyard onto the battlefield under your control. That creature is black and is a Nightmare in addition to its other creature types.
When Chainer leaves the battlefield, exile all Nightmares.

Demon of Wailing Agonies

Flying
Lieutenant — As long as you control your commander, this creature gets +2/+2 and has "Whenever this creature deals combat damage to a player, that player sacrifices a creature of their choice."

Rakdos, the Showstopper

Flying, trample
When Rakdos enters, flip a coin for each creature that isn't a Demon, Devil, or Imp. Destroy each creature whose coin comes up tails.

Revel in Riches

Whenever a creature an opponent controls dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
At the beginning of your upkeep, if you control ten or more Treasures, you win the game.

Reiver Demon

Flying
When this creature enters, if you cast it from your hand, destroy all nonartifact, nonblack creatures. They can't be regenerated.

Whisper, Blood Liturgist

{T}, Sacrifice two creatures: Return target creature card from your graveyard to the battlefield.

Animate Dead

Enchant creature card in a graveyard
When this Aura enters, if it's on the battlefield, it loses "enchant creature card in a graveyard" and gains "enchant creature put onto the battlefield with this Aura." Return enchanted creature card to the battlefield under your control and attach this Aura to it. When this Aura leaves the battlefield, that creature's controller sacrifices it.
Enchanted creature gets -1/-0.

Xathrid Demon

Flying, trample
At the beginning of your upkeep, sacrifice a creature other than this creature, then each opponent loses life equal to the sacrificed creature's power. If you can't sacrifice a creature, tap this creature and you lose 7 life.

Bloodgift Demon

Flying
At the beginning of your upkeep, target player draws a card and loses 1 life.

Demonlord Belzenlok

Flying, trample
When Demonlord Belzenlok enters, exile cards from the top of your library until you exile a nonland card, then put that card into your hand. If the card's mana value is 4 or greater, repeat this process. Demonlord Belzenlok deals 1 damage to you for each card put into your hand this way.

Shadowborn Demon

Flying
When this creature enters, destroy target non-Demon creature.
At the beginning of your upkeep, if there are fewer than six creature cards in your graveyard, sacrifice a creature.

Rakdos, Lord of Riots

You can't cast Rakdos unless an opponent lost life this turn.
Flying, trample
Creature spells you cast cost {1} less to cast for each 1 life your opponents have lost this turn.

Demon of Dark Schemes

Flying
When Demon of Dark Schemes enters, all other creatures get -2/-2 until end of turn.
Whenever another creature dies, you get {E} (an energy counter).
{2}{B}, Pay {E}{E}{E}{E}: Put target creature card from a graveyard onto the battlefield under your control tapped.

Black Market

Whenever a creature dies, put a charge counter on this enchantment.
At the beginning of your first main phase, add {B} for each charge counter on this enchantment.

Demon of Catastrophes

As an additional cost to cast this spell, sacrifice a creature.
Flying, trample

Woebringer Demon

Flying
At the beginning of each player's upkeep, that player sacrifices a creature of their choice. If the player can't, sacrifice this creature.

Pestilence Demon

Flying
{B}: This creature deals 1 damage to each creature and each player.

Archfiend's Vessel

Lifelink (Damage dealt by this creature also causes you to gain that much life.)
When this creature enters, if it entered from your graveyard or you cast it from your graveyard, exile it. If you do, create a 5/5 black Demon creature token with flying.