Ancient Cellarspawn

Each spell you cast that's a Demon, Horror, or Nightmare costs {1} less to cast.
Whenever you cast a spell, if the amount of mana spent to cast it was less than its mana value, target opponent loses life equal to the difference.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Liliana's Contract

When Liliana's Contract enters, you draw four cards and you lose 4 life.
At the beginning of your upkeep, if you control four or more Demons with different names, you win the game.

Rakdos, the Showstopper

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

Rakdos Charm

Choose one —
• Exile target player's graveyard.
• Destroy target artifact.
• Each creature deals 1 damage to its controller.

Ob Nixilis, Unshackled

Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature of their choice and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis, Unshackled.

Patriarch's Bidding

Each player chooses a creature type. Each player returns all creature cards of a type chosen this way from their graveyard to the battlefield.

Rune-Scarred Demon

Flying
When this creature enters, search your library for a card, put it into your hand, then shuffle.

Raphael, Fiendish Savior

Flying
Other Demons, Devils, Imps, and Tieflings you control get +1/+1 and have lifelink.
At the beginning of each end step, if a creature card was put into your graveyard from anywhere this turn, create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."

Bloodgift Demon

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

Spawn of Mayhem

Spectacle {1}{B}{B} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Flying, trample
At the beginning of your upkeep, Spawn of Mayhem deals 1 damage to each player. Then if you have 10 or less life, put a +1/+1 counter on Spawn of Mayhem.

Thermo-Alchemist

Defender
{T}: Thermo-Alchemist deals 1 damage to each opponent.
Whenever you cast an instant or sorcery spell, untap Thermo-Alchemist.

Séance Board

Morbid — At the beginning of each end step, if a creature died this turn, put a soul counter on Séance Board.
{T}: Add X mana of any one color, where X is the number of soul counters on Séance Board. Spend this mana only to cast instant, sorcery, Demon, and Spirit spells.

Orcus, Prince of Undeath

Flying, trample
When Orcus, Prince of Undeath enters, choose one —
• Each other creature gets -X/-X until end of turn. You lose X life.
• Return up to X target creature cards with total mana value X or less from your graveyard to the battlefield. They gain haste until end of turn.

Herald of Slaanesh

Locus of Slaanesh — Demon spells you cast cost {2} less to cast.
Other Demons you control have haste.

The Lord of Pain

Menace
Your opponents can't gain life.
Whenever a player casts their first spell each turn, choose another target player. The Lord of Pain deals damage equal to that spell's mana value to the chosen player.

Rakdos, Lord of Riots

You can't cast Rakdos, Lord of Riots 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.

Anger

Haste
As long as Anger is in your graveyard and you control a Mountain, creatures you control have haste.

Sin Prodder

Menace
At the beginning of your upkeep, reveal the top card of your library. Any opponent may have you put that card into your graveyard. If a player does, Sin Prodder deals damage to that player equal to that card's mana value. Otherwise, put that card into your hand.

Electrostatic Field

Defender
Whenever you cast an instant or sorcery spell, Electrostatic Field deals 1 damage to each opponent.

Bloodletter of Aclazotz

Flying
If an opponent would lose life during your turn, they lose twice that much life instead. (Damage causes loss of life.)

Kaervek the Merciless

Whenever an opponent casts a spell, Kaervek the Merciless deals damage equal to that spell's mana value to any target.

Rakdos, Patron of Chaos

Flying, trample
At the beginning of your end step, target opponent may sacrifice two nonland, nontoken permanents of their choice. If they don't, you draw two cards.

Terminate

Destroy target creature. It can't be regenerated.

Spear Spewer

Defender
{T}: Spear Spewer deals 1 damage to each player.

Lobber Crew

Defender
{T}: Lobber Crew deals 1 damage to each opponent.
Whenever you cast a multicolored spell, untap Lobber Crew.

Valgavoth, Harrower of Souls

Flying
Ward—Pay 2 life.
Whenever an opponent loses life for the first time during each of their turns, put a +1/+1 counter on Valgavoth, Harrower of Souls and draw a card.

Haunting Voyage

Choose a creature type. Return up to two creature cards of that type from your graveyard to the battlefield. If this spell was foretold, return all creature cards of that type from your graveyard to the battlefield instead.
Foretell {5}{B}{B} (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.)

Indulgent Tormentor

Flying
At the beginning of your upkeep, draw a card unless target opponent sacrifices a creature of their choice or pays 3 life.

Creeping Bloodsucker

At the beginning of your upkeep, Creeping Bloodsucker deals 1 damage to each opponent. You gain life equal to the damage dealt this way.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Unruly Catapult

Defender
{T}: Unruly Catapult deals 1 damage to each opponent.
Whenever you cast an instant or sorcery spell, untap Unruly Catapult.

Rakdos Drake

Flying
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.)

Blazemire Verge

{T}: Add {B}.
{T}: Add {R}. Activate only if you control a Swamp or a Mountain.

Harvester of Souls

Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Whenever another nontoken creature dies, you may draw a card.