Hearthborn Battler

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

Eidolon of the Great Revel

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

Painful Quandary

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.

Kambal, Consul of Allocation

Whenever an opponent casts a noncreature spell, that player loses 2 life and you gain 2 life.

Gleeful Arsonist

Whenever an opponent casts a noncreature spell, this creature deals damage equal to its power to that player.
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Curse of Wizardry

As this enchantment enters, choose a color.
Whenever a player casts a spell of the chosen color, that player loses 1 life.

Liesa, Shroud of Dusk

Rather than pay {2} for each previous time you've cast this spell from the command zone this game, pay 2 life that many times.
Flying, lifelink
Whenever a player casts a spell, they lose 2 life.

Magebane Lizard

Whenever a player casts a noncreature spell, this creature deals damage to that player equal to the number of noncreature spells they've cast this turn.

The Lord of Pain

Menace
Your opponents can't gain life.
Whenever a player casts their first spell each turn, choose another target player. The Lord of Pain deals damage equal to that spell's mana value to the chosen player.

Pyrostatic Pillar

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

Isolation Cell

Whenever an opponent casts a creature spell, that player loses 2 life unless they pay {2}.

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.

Thought Prison

Imprint — When this artifact enters, you may have target player reveal their hand. If you do, choose a nonland card from it and exile that card.
Whenever a player casts a spell that shares a color or mana value with the exiled card, this artifact deals 2 damage to that player.

Adrenaline Jockey

Whenever a player casts a spell, if it's not their turn, this creature deals 4 damage to them.
Whenever you activate an exhaust ability, put a +1/+1 counter on this creature.

Spellshock

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

Scytheclaw Raptor

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

Curse of Shaken Faith

Enchant player
Whenever enchanted player casts a spell other than the first spell they cast each turn or copies a spell, this Aura deals 2 damage to them.

Scab-Clan Berserker

Haste
Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever an opponent casts a noncreature spell, if this creature is renowned, this creature deals 2 damage to that player.

Rug of Smothering

Flying
Whenever a player casts a spell, they lose 1 life for each spell they've cast this turn.