Act of Treason

Gain control of target creature until end of turn. Untap that creature. It gains haste until end of turn. (It can attack and {T} this turn.)

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.

Swamp

Body Dropper

Whenever you sacrifice another creature, put a +1/+1 counter on Body Dropper.
{B}{R}, Sacrifice another creature: Body Dropper gains menace until end of turn. (It can't be blocked except by two or more creatures.)

Hobblefiend

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
{1}, Sacrifice another creature: Put a +1/+1 counter on Hobblefiend.

Witty Roastmaster

Alliance — Whenever another creature you control enters, Witty Roastmaster deals 1 damage to each opponent.

Rakdos Cackler

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.)

Devilish Valet

Trample, haste
Alliance — Whenever another creature you control enters, double Devilish Valet's power until end of turn.

Dance with Devils

Create two 1/1 red Devil creature tokens. They have "When this creature dies, it deals 1 damage to any target."

Make Mischief

Make Mischief deals 1 damage to any target. Create a 1/1 red Devil creature token. It has "When this creature dies, it deals 1 damage to any target."

Footlight Fiend

When Footlight Fiend dies, it deals 1 damage to any target.

Bone Splinters

As an additional cost to cast this spell, sacrifice a creature.
Destroy target creature.

Frenzied Devils

Haste
Whenever you cast a noncreature spell, Frenzied Devils gets +2/+2 until end of turn.

Mountain

Devil's Play

Devil's Play deals X damage to any target.
Flashback {X}{R}{R}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Wrangle

Gain control of target creature with power 4 or less until end of turn. Untap that creature. It gains haste until end of turn.

Killing Wave

For each creature, its controller sacrifices it unless they pay X life.

Vexing Devil

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

Raise Dead

Return target creature card from your graveyard to your hand.

Spiteful Prankster

During your turn, Spiteful Prankster has first strike.
Whenever another creature dies, Spiteful Prankster deals 1 damage to target player or planeswalker.

Blood Crypt

({T}: Add {B} or {R}.)
As Blood Crypt enters, you may pay 2 life. If you don't, it enters tapped.

Mayhem Devil

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

Sulfurous Springs

{T}: Add {C}.
{T}: Add {B} or {R}. Sulfurous Springs deals 1 damage to you.

Devils' Playground

Create four 1/1 red Devil creature tokens. They have "When this creature dies, it deals 1 damage to any target."

Flayer of the Hatebound

Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)
Whenever Flayer of the Hatebound or another creature enters from your graveyard, that creature deals damage equal to its power to any target.

Village Rites

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Angrath's Rampage

Choose one —
• Target player sacrifices an artifact of their choice.
• Target player sacrifices a creature of their choice.
• Target player sacrifices a planeswalker of their choice.

Aid the Fallen

Choose one or both —
• Return target creature card from your graveyard to your hand.
• Return target planeswalker card from your graveyard to your hand.

Festival Crasher

Whenever you cast an instant or sorcery spell, Festival Crasher gets +2/+0 until end of turn.

Zariel, Archduke of Avernus

+1: Creatures you control get +1/+0 and gain haste until end of turn.
0: Create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."
−6: You get an emblem with "At the end of the first combat phase on your turn, untap target creature you control. After this phase, there is an additional combat phase."

Ob Nixilis, the Adversary

Casualty X. The copy isn't legendary and has starting loyalty X. (As you cast this spell, you may sacrifice a creature with power X. When you do, copy this spell. The copy becomes a token.)
+1: Each opponent loses 2 life unless they discard a card. If you control a Demon or Devil, you gain 2 life.
−2: Create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."
−7: Target player draws seven cards and loses 7 life.

Furnace Reins

Gain control of target creature until end of turn. Untap that creature. Until end of turn, it gains haste and "Whenever this creature deals combat damage to a player or battle, create a Treasure token." (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Devil

When this creature dies, it deals 1 damage to any target.

Havoc Jester

Whenever you sacrifice a permanent, Havoc Jester deals 1 damage to any target.

Fiendish Duo

First strike (This creature deals combat damage before creatures without first strike.)
If a source would deal damage to an opponent, it deals double that damage to that player instead.

Light Up the Stage

Spectacle {R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Exile the top two cards of your library. Until the end of your next turn, you may play those cards.

Charmbreaker Devils

At the beginning of your upkeep, return an instant or sorcery card at random from your graveyard to your hand.
Whenever you cast an instant or sorcery spell, Charmbreaker Devils gets +4/+0 until end of turn.

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.

Pugnacious Pugilist

Whenever Pugnacious Pugilist attacks, create a tapped and attacking 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."
Blitz {3}{R} (If you cast this spell for its blitz cost, it gains haste and "When this creature dies, draw a card." Sacrifice it at the beginning of the next end step.)

Burn Down the House

Choose one —
• Burn Down the House deals 5 damage to each creature and each planeswalker.
• Create three 1/1 red Devil creature tokens with "When this creature dies, it deals 1 damage to any target." They gain haste until end of turn.

Rakdos Headliner

Haste
Echo—Discard a card. (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)

Bedlam Reveler

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.
Prowess
When Bedlam Reveler enters, discard your hand, then draw three cards.

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.

Kari Zev's Expertise

Gain control of target creature or Vehicle until end of turn. Untap it. It gains haste until end of turn.
You may cast a spell with mana value 2 or less from your hand without paying its mana cost.

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.