Manabarbs

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

Burning Earth

Whenever a player taps a nonbasic land for mana, this enchantment deals 1 damage to that player.

Steam Vines

Enchant land
When enchanted land becomes tapped, destroy it and this Aura deals 1 damage to that land's controller. That player attaches this Aura to a land of their choice.

Dingus Egg

Whenever a land is put into a graveyard from the battlefield, this artifact deals 2 damage to that land's controller.

Ankh of Mishra

Whenever a land enters, this artifact deals 2 damage to that land's controller.

Zo-Zu the Punisher

Whenever a land enters, Zo-Zu deals 2 damage to that land's controller.

Harsh Mentor

Whenever an opponent activates an ability of an artifact, creature, or land on the battlefield, if it isn't a mana ability, this creature deals 2 damage to that player.

Scald

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

Domri, Anarch of Bolas

Creatures you control get +1/+0.
+1: Add {R} or {G}. Creature spells you cast this turn can't be countered.
−2: Target creature you control fights target creature you don't control.

Cemetery Gatekeeper

First strike
When this creature enters, exile a card from a graveyard.
Whenever a player plays a land or casts a spell, if it shares a card type with the exiled card, this creature deals 2 damage to that player.

Overabundance

Whenever a player taps a land for mana, that player adds one mana of any type that land produced, and this enchantment deals 1 damage to the player.

Tunnel Ignus

Whenever a land enters under an opponent's control, if that player had another land enter the battlefield under their control this turn, this creature deals 3 damage to that player.