Manabarbs

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

Spiteful Visions

At the beginning of each player's draw step, that player draws an additional card.
Whenever a player draws a card, Spiteful Visions deals 1 damage to that player.

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.

Last Laugh

Whenever a permanent other than Last Laugh is put into a graveyard from the battlefield, Last Laugh deals 1 damage to each creature and each player.
When no creatures are on the battlefield, sacrifice Last Laugh.

Dwarven Shrine

Whenever a player casts a spell, Dwarven Shrine deals X damage to that player, where X is twice the number of cards in all graveyards with the same name as that spell.

Sunspine Lynx

Players can't gain life.
Damage can't be prevented.
When Sunspine Lynx enters, it deals damage to each player equal to the number of nonbasic lands that player controls.

Mogis, God of Slaughter

Indestructible
As long as your devotion to black and red is less than seven, Mogis isn't a creature.
At the beginning of each opponent's upkeep, Mogis deals 2 damage to that player unless they sacrifice a creature of their choice.

Screaming Nemesis

Haste
Whenever Screaming Nemesis is dealt damage, it deals that much damage to any other target. If a player is dealt damage this way, they can't gain life for the rest of the game.

Harsh Mentor

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

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.

Psychogenic Probe

Whenever a spell or ability causes a player to shuffle their library, Psychogenic Probe deals 2 damage to that player.

Plague Spitter

At the beginning of your upkeep, Plague Spitter deals 1 damage to each creature and each player.
When Plague Spitter dies, it deals 1 damage to each creature and each player.

Rampaging Ferocidon

Menace
Players can't gain life.
Whenever another creature enters, Rampaging Ferocidon deals 1 damage to that creature's controller.

Seizures

Enchant creature
Whenever enchanted creature becomes tapped, Seizures deals 3 damage to that creature's controller unless that player pays {3}.

Underworld Dreams

Whenever an opponent draws a card, Underworld Dreams deals 1 damage to that player.

Immolation Shaman

Whenever an opponent activates an ability of an artifact, creature, or land that isn't a mana ability, Immolation Shaman deals 1 damage to that player.
{3}{R}{R}: Immolation Shaman gets +3/+3 and gains menace until end of turn.

Fate Unraveler

Whenever an opponent draws a card, Fate Unraveler deals 1 damage to that player.

Cemetery Gatekeeper

First strike
When Cemetery Gatekeeper 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, Cemetery Gatekeeper deals 2 damage to that player.

Steam Vines

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

Burning Earth

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

Obosh, the Preypiercer

Companion — Your starting deck contains only cards with odd mana values and land cards. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
If a source you control with an odd mana value would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Scytheclaw Raptor

Whenever a player casts a spell, if it's not their turn, Scytheclaw Raptor deals 4 damage to them.

Ob Nixilis, the Hate-Twisted

Whenever an opponent draws a card, Ob Nixilis, the Hate-Twisted deals 1 damage to that player.
−2: Destroy target creature. Its controller draws two cards.

Spellshock

Whenever a player casts a spell, Spellshock deals 2 damage to that player.

Ash Zealot

First strike, haste
Whenever a player casts a spell from a graveyard, Ash Zealot deals 3 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.

Hearthborn Battler

Haste
Whenever a player casts their second spell each turn, Hearthborn Battler deals 2 damage to target opponent.

Haunting Wind

Whenever an artifact becomes tapped or a player activates an artifact's ability without {T} in its activation cost, Haunting Wind deals 1 damage to that artifact's controller.