Soul Immolation

As an additional cost to cast this spell, blight X. X can't be greater than the greatest toughness among creatures you control. (Put X -1/-1 counters on a creature you control.)
Soul Immolation deals X damage to each opponent and each creature they control.

Earthquake

Earthquake deals X damage to each creature without flying and each player.

Demon's Disciple

When this creature enters, each player sacrifices a creature or planeswalker of their choice.

Price of Progress

Price of Progress deals damage to each player equal to twice the number of nonbasic lands that player controls.

Snort

Each player may discard their hand and draw five cards. Then Snort deals 5 damage to each opponent who discarded their hand this way.
Flashback {5}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Acidic Soil

Acidic Soil deals damage to each player equal to the number of lands they control.

Grab the Prize

As an additional cost to cast this spell, discard a card.
Draw two cards. If the discarded card wasn't a land card, Grab the Prize deals 2 damage to each opponent.

Prisoner's Dilemma

Each opponent secretly chooses silence or snitch, then the choices are revealed. If each opponent chose silence, Prisoner's Dilemma deals 4 damage to each of them. If each opponent chose snitch, Prisoner's Dilemma deals 8 damage to each of them. Otherwise, Prisoner's Dilemma deals 12 damage to each opponent who chose silence.
Flashback {5}{R}{R}

Boltwave

Boltwave deals 3 damage to each opponent.

Volcanic Fallout

This spell can't be countered.
Volcanic Fallout deals 2 damage to each creature and each player.

Chain Devil

Animate Chains — When this creature enters, each player sacrifices a nontoken creature of their choice.

Abyssal Gatekeeper

When this creature dies, each player sacrifices a creature of their choice.

Steam Blast

Steam Blast deals 2 damage to each creature and each player.

Champion of the Path

As an additional cost to cast this spell, behold an Elemental and exile it. (Exile an Elemental you control or an Elemental card from your hand.)
Whenever another Elemental you control enters, it deals damage equal to its power to each opponent.
When this creature leaves the battlefield, return the exiled card to its owner's hand.

Hostility

Haste
If a spell you control would deal damage to an opponent, prevent that damage. Create a 3/1 red Elemental Shaman creature token with haste for each 1 damage prevented this way.
When Hostility is put into a graveyard from anywhere, shuffle it into its owner's library.

Vicious Rumors

Vicious Rumors deals 1 damage to each opponent. Each opponent discards a card, then mills a card. You gain 1 life.

Fleshbag Marauder

When this creature enters, each player sacrifices a creature of their choice.

Gravelighter

Flying
When this creature enters, draw a card if a creature died this turn. Otherwise, each player sacrifices a creature of their choice.

Ghostfire Slice

Devoid (This card has no color.)
This spell costs {2} less to cast if an opponent controls a multicolored permanent.
Ghostfire Slice deals 4 damage to any target.

Lagomos, Hand of Hatred

At the beginning of combat on your turn, create a 2/1 red Elemental creature token with trample and haste. Sacrifice it at the beginning of the next end step.
{T}: Search your library for a card, put it into your hand, then shuffle. Activate only if five or more creatures died this turn.

Slum Reaper

Accursed Marauder

When this creature enters, each player sacrifices a nontoken creature of their choice.

Creeping Chill

Creeping Chill deals 3 damage to each opponent and you gain 3 life.
When Creeping Chill is put into your graveyard from your library, you may exile it. If you do, Creeping Chill deals 3 damage to each opponent and you gain 3 life.

Breath of Malfegor

Breath of Malfegor deals 5 damage to each opponent.

Sizzle

Merciless Executioner

Ruinous Rampage

Choose one —
• Ruinous Rampage deals 3 damage to each opponent.
• Exile all artifacts with mana value 3 or less.

Slagstorm

Choose one —
• Slagstorm deals 3 damage to each creature.
• Slagstorm deals 3 damage to each player.

Fiery Confluence

Choose three. You may choose the same mode more than once.
• Fiery Confluence deals 1 damage to each creature.
• Fiery Confluence deals 2 damage to each opponent.
• Destroy target artifact.

Plaguecrafter

When this creature enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.