Disembowel

Destroy target creature with mana value X.

Skullcrack

Players can't gain life this turn. Damage can't be prevented this turn. Skullcrack deals 3 damage to target player or planeswalker.

Dreadbore

Smash

Theater of Horrors

At the beginning of your upkeep, exile the top card of your library.
During your turn, if an opponent lost life this turn, you may play lands and cast spells from among cards exiled with Theater of Horrors.
{3}{R}: Theater of Horrors deals 1 damage to target opponent or planeswalker.

Lacerate Flesh

Lacerate Flesh deals 4 damage to target creature. Create a number of Blood tokens equal to the amount of excess damage dealt to that creature this way. (They're artifacts with "{1}, {T}, Discard a card, Sacrifice this artifact: Draw a card.")

Mugging

Mugging deals 2 damage to target creature. That creature can't block this turn.

Auger Spree

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

Morgue Burst

Return target creature card from your graveyard to your hand. Morgue Burst deals damage to any target equal to the power of the card returned this way.

Havoc Festival

Players can't gain life.
At the beginning of each player's upkeep, that player loses half their life, rounded up.

Skull Rend

Skull Rend deals 2 damage to each opponent. Those players each discard two cards at random.

Rakdos Shred-Freak

Grisly Ritual

Destroy target creature or planeswalker. Create two Blood tokens. (They're artifacts with "{1}, {T}, Discard a card, Sacrifice this artifact: Draw a card.")

Defenestrate

Instill Furor

Enchant creature
Enchanted creature has "At the beginning of your end step, sacrifice this creature unless it attacked this turn."

Cavalcade of Calamity

Whenever a creature you control with power 1 or less attacks, Cavalcade of Calamity deals 1 damage to the player or planeswalker that creature is attacking.

Ragefire

Ragefire deals 3 damage to target creature.

Rage Thrower

Whenever another creature dies, Rage Thrower deals 2 damage to target player or planeswalker.

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.

Blood Funnel

Noncreature spells you cast cost {2} less to cast.
Whenever you cast a noncreature spell, counter that spell unless you sacrifice a creature.

Breath of Fury

Enchant creature you control
When enchanted creature deals combat damage to a player, sacrifice it and attach Breath of Fury to a creature you control. If you do, untap all creatures you control and after this phase, there is an additional combat phase.

Skewer the Critics

Spectacle {R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Skewer the Critics deals 3 damage to any target.

Bedevil

Destroy target artifact, creature, or planeswalker.

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.

Macabre Mockery

Put target creature card from an opponent's graveyard onto the battlefield under your control. It gets +2/+0 and gains haste until end of turn. Sacrifice it at the beginning of the next end step.

Drill Bit

Spectacle {B} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Target player reveals their hand. You choose a nonland card from it. That player discards that card.

Wrecking Ogre

Double strike
Bloodrush — {3}{R}{R}, Discard Wrecking Ogre: Target attacking creature gets +3/+3 and gains double strike until end of turn.

Ceremonial Knife

Equipped creature gets +1/+0 and has "Whenever this creature deals combat damage, create a Blood token." (It's an artifact with "{1}, {T}, Discard a card, Sacrifice this artifact: Draw a card.")
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Infernal Grasp

Destroy target creature. You lose 2 life.

Into the Maw of Hell

Destroy target land. Into the Maw of Hell deals 13 damage to target creature.

Slaughter Games

This spell can't be countered.
Choose a nonland card name. Search target opponent's graveyard, hand, and library for any number of cards with that name and exile them. Then that player shuffles.