Kessig Flamebreather

Whenever you cast a noncreature spell, Kessig Flamebreather deals 1 damage to each opponent.

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.

Crypt Ghast

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Whenever you tap a Swamp for mana, add an additional {B}.

All Will Be One

Whenever you put one or more counters on a permanent or player, All Will Be One deals that much damage to target opponent, creature an opponent controls, or planeswalker an opponent controls.

Underworld Dreams

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

Bontu's Monument

Black creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.

Trespasser's Curse

Enchant player
Whenever a creature enchanted player controls enters, that player loses 1 life and you gain 1 life.

Chandra, Awakened Inferno

This spell can't be countered.
+2: Each opponent gets an emblem with "At the beginning of your upkeep, this emblem deals 1 damage to you."
−3: Chandra, Awakened Inferno deals 3 damage to each non-Elemental creature.
−X: Chandra, Awakened Inferno deals X damage to target creature or planeswalker. If a permanent dealt damage this way would die this turn, exile it instead.

Ob Nixilis, Captive Kingpin

Flying, trample
Whenever one or more opponents each lose exactly 1 life, put a +1/+1 counter on Ob Nixilis, Captive Kingpin. Exile the top card of your library. Until your next end step, you may play that card.

Creeping Bloodsucker

At the beginning of your upkeep, Creeping Bloodsucker deals 1 damage to each opponent. You gain life equal to the damage dealt this way.

Kederekt Parasite

Whenever an opponent draws a card, if you control a red permanent, you may have Kederekt Parasite deal 1 damage to that player.

Revenge of Ravens

Whenever a creature attacks you or a planeswalker you control, that creature's controller loses 1 life and you gain 1 life.

Hissing Miasma

Whenever a creature attacks you, its controller loses 1 life.

Firebrand Archer

Whenever you cast a noncreature spell, Firebrand Archer deals 1 damage to each opponent.