Impatience

At the beginning of each player's end step, if that player didn't cast a spell this turn, Impatience deals 2 damage to that player.

The Red Terror

Advanced Species — Whenever a red source you control deals damage to one or more permanents and/or players, put a +1/+1 counter on The Red Terror.

Citadel of Pain

At the beginning of each player's end step, Citadel of Pain deals X damage to that player, where X is the number of untapped lands they control.

Enchanter's Bane

At the beginning of your end step, target enchantment deals damage equal to its mana value to its controller unless that player sacrifices it.

Heat of Battle

Whenever a creature blocks, Heat of Battle deals 1 damage to that creature's controller.

Scald

Whenever a player taps an Island for mana, Scald deals 1 damage to that player.

Flame Blitz

At the beginning of your end step, Flame Blitz deals 5 damage to each planeswalker.
Cycling {2} ({2}, Discard this card: Draw a card.)

Close Quarters

Whenever a creature you control becomes blocked, Close Quarters deals 1 damage to any target.

Manabarbs

Whenever a player taps a land for mana, Manabarbs deals 1 damage to that player.

Aether Sting

Whenever an opponent casts a creature spell, Aether Sting deals 1 damage to that player.

Battle Strain

Whenever a creature blocks, Battle Strain deals 1 damage to that creature's controller.

Forgeborn Oreads

Constellation — Whenever Forgeborn Oreads or another enchantment you control enters, Forgeborn Oreads deals 1 damage to any target.

Bloodfire Infusion

Enchant creature you control
{R}, Sacrifice enchanted creature: Bloodfire Infusion deals damage equal to the sacrificed creature's power to each creature.

Insolence

Enchant creature
Whenever enchanted creature becomes tapped, Insolence deals 2 damage to that creature's controller.

Court of Ire

When Court of Ire enters, you become the monarch.
At the beginning of your upkeep, Court of Ire deals 2 damage to any target. If you're the monarch, it deals 7 damage instead.

Aether Flash

Whenever a creature enters, Aether Flash deals 2 damage to it.

Burning Earth

Whenever a player taps a nonbasic land for mana, Burning Earth deals 1 damage to that player.

Pyrostatic Pillar

Whenever a player casts a spell with mana value 3 or less, Pyrostatic Pillar deals 2 damage to that player.

Curse of the Pierced Heart

Enchant player
At the beginning of enchanted player's upkeep, Curse of the Pierced Heart deals 1 damage to that player or a planeswalker that player controls.

Roiling Vortex

At the beginning of each player's upkeep, Roiling Vortex deals 1 damage to them.
Whenever a player casts a spell, if no mana was spent to cast that spell, Roiling Vortex deals 5 damage to that player.
{R}: Your opponents can't gain life this turn.

Dictate of the Twin Gods

Flash
If a source would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Circle of Flame

Whenever a creature without flying attacks you or a planeswalker you control, Circle of Flame deals 1 damage to that creature.

Gratuitous Violence

If a creature you control would deal damage to a permanent or player, it deals double that damage instead.

Eidolon of the Great Revel

Whenever a player casts a spell with mana value 3 or less, Eidolon of the Great Revel deals 2 damage to that player.

Repercussion

Whenever a creature is dealt damage, Repercussion deals that much damage to that creature's controller.

Antagonism

At the beginning of each player's end step, Antagonism deals 2 damage to that player unless one of their opponents was dealt damage this turn.

Ancient Runes

At the beginning of each player's upkeep, Ancient Runes deals damage to that player equal to the number of artifacts they control.

Honden of Infinite Rage

At the beginning of your upkeep, Honden of Infinite Rage deals damage to any target equal to the number of Shrines you control.

Fiery Emancipation

If a source you control would deal damage to a permanent or player, it deals triple that damage to that permanent or player instead.

Leyline of Combustion

If Leyline of Combustion is in your opening hand, you may begin the game with it on the battlefield.
Whenever you and/or at least one permanent you control becomes the target of a spell or ability an opponent controls, Leyline of Combustion deals 2 damage to that player.

Maddening Hex

Enchant player
Whenever enchanted player casts a noncreature spell, roll a d6. Maddening Hex deals damage to that player equal to the result. Then attach Maddening Hex to another one of your opponents chosen at random.

Burning Anger

Enchant creature
Enchanted creature has "{T}: This creature deals damage equal to its power to any target."