Rakdos, Lord of Riots

You can't cast this spell 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.

Balor

Flying
Whenever Balor attacks or dies, choose one or more. Each mode must target a different player.
• Target opponent draws three cards, then discards three cards at random.
• Target opponent sacrifices a nontoken artifact.
• Balor deals damage to target opponent equal to the number of cards in their hand.

Mountain

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."

Pilfering Imp

Flying
{1}{B}, {T}, Sacrifice Pilfering Imp: Target opponent reveals their hand. You choose a nonland card from it. That player discards that card. Activate only as a sorcery.

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.

Dragonskull Summit

Dragonskull Summit enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Hellrider

Haste
Whenever a creature you control attacks, Hellrider deals 1 damage to the player or planeswalker it's attacking.

Aspiring Champion

Menace
Ruinous Ascension — When Aspiring Champion deals combat damage to a player, sacrifice it. If you do, reveal cards from the top of your library until you reveal a creature card. Put that card onto the battlefield, then shuffle the rest into your library. If that creature is a Demon, it deals damage equal to its power to each opponent.

Bloodcrusher of Khorne

Trample
Devastating Charge — Other creatures you control have trample.

Mayhem Devil

Whenever a player sacrifices a permanent, Mayhem Devil deals 1 damage to any target.

Vexing Devil

When Vexing Devil enters, any opponent may have it deal 4 damage to them. If a player does, sacrifice Vexing Devil.

Swamp

Reaper from the Abyss

Flying
Morbid — At the beginning of each end step, if a creature died this turn, destroy target non-Demon creature.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Rakdos Signet

Dreadfeast Demon

Flying
At the beginning of your end step, sacrifice a non-Demon creature. If you do, create a token that's a copy of Dreadfeast Demon.

Varragoth, Bloodsky Sire

Deathtouch
Boast — {1}{B}: Target player searches their library for a card, then shuffles and puts that card on top. (Activate only if this creature attacked this turn and only once each turn.)