Hellfire Mongrel

At the beginning of each opponent's upkeep, if that player has two or fewer cards in hand, Hellfire Mongrel deals 2 damage to that player.

Sudden Demise

Choose a color. Sudden Demise deals X damage to each creature of the chosen color.

Demanding Dragon

Flying
When Demanding Dragon enters, it deals 5 damage to target opponent unless that player sacrifices a creature of their choice.

Cinder Pyromancer

{T}: Cinder Pyromancer deals 1 damage to target player or planeswalker.
Whenever you cast a red spell, you may untap Cinder Pyromancer.

Cyclops Gladiator

Whenever Cyclops Gladiator attacks, you may have it deal damage equal to its power to target creature defending player controls. If you do, that creature deals damage equal to its power to Cyclops Gladiator.

Shivan Hellkite

Flying (This creature can't be blocked except by creatures with flying or reach.)
{1}{R}: Shivan Hellkite deals 1 damage to any target.

Kamahl, Pit Fighter

Haste (This creature can attack and {T} as soon as it comes under your control.)
{T}: Kamahl, Pit Fighter deals 3 damage to any target.

Moonglove Extract

Sacrifice Moonglove Extract: It deals 2 damage to any target.

Spitting Earth

Spitting Earth deals damage to target creature equal to the number of Mountains you control.

Crater's Claws

Crater's Claws deals X damage to any target.
Ferocious — Crater's Claws deals X plus 2 damage instead if you control a creature with power 4 or greater.

Lightning Strike

Lightning Strike deals 3 damage to any target.

Shock

Bogardan Hellkite

Flash
Flying
When Bogardan Hellkite enters, it deals 5 damage divided as you choose among any number of targets.

Somberwald Vigilante

Whenever Somberwald Vigilante becomes blocked by a creature, Somberwald Vigilante deals 1 damage to that creature.

Deathforge Shaman

Multikicker {R} (You may pay an additional {R} any number of times as you cast this spell.)
When Deathforge Shaman enters, it deals damage to target player or planeswalker equal to twice the number of times it was kicked.

Seismic Strike

Seismic Strike deals damage to target creature equal to the number of Mountains you control.

Seething Song

Mizzium Mortars

Mizzium Mortars deals 4 damage to target creature you don't control.
Overload {3}{R}{R}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Kumano, Master Yamabushi

{1}{R}: Kumano, Master Yamabushi deals 1 damage to any target.
If a creature dealt damage by Kumano this turn would die, exile it instead.

Vulshok Replica

{1}{R}, Sacrifice Vulshok Replica: It deals 3 damage to target player or planeswalker.

Cosi's Ravager

Landfall — Whenever a land you control enters, you may have Cosi's Ravager deal 1 damage to target player or planeswalker.

Forge Devil

When Forge Devil enters, it deals 1 damage to target creature and 1 damage to you.

Rage of Purphoros

Rage of Purphoros deals 4 damage to target creature. It can't be regenerated this turn. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Fire Servant

If a red instant or sorcery spell you control would deal damage, it deals double that damage instead.

Prodigal Pyromancer

{T}: Prodigal Pyromancer deals 1 damage to any target.

Flame Slash

Flame Slash deals 4 damage to target creature.

Mountain

Searing Blood

Searing Blood deals 2 damage to target creature. When that creature dies this turn, Searing Blood deals 3 damage to the creature's controller.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Chandra Nalaar

+1: Chandra Nalaar deals 1 damage to target player or planeswalker.
−X: Chandra Nalaar deals X damage to target creature.
−8: Chandra Nalaar deals 10 damage to target player or planeswalker and each creature that player or that planeswalker's controller controls.