Warstorm Surge

Whenever a creature you control enters, it deals damage equal to its power to any target.

Blazing Salvo

Blazing Salvo deals 3 damage to target creature unless that creature's controller has Blazing Salvo deal 5 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, Curse of Shaken Faith deals 2 damage to them.

Sol Ring

Mechanized Warfare

If a red or artifact source you control would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 1 instead.

Sulfuric Vortex

At the beginning of each player's upkeep, Sulfuric Vortex deals 2 damage to that player.
If a player would gain life, that player gains no life instead.

Silent Arbiter

No more than one creature can attack each combat.
No more than one creature can block each combat.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Skullclamp

Equipped creature gets +1/-1.
Whenever equipped creature dies, draw two cards.
Equip {1}

Impact Tremors

Whenever a creature you control enters, Impact Tremors deals 1 damage to each opponent.

Norin the Wary

When a player casts a spell or a creature attacks, exile Norin the Wary. Return it to the battlefield under its owner's control at the beginning of the next end step.

Faithless Looting

Draw two cards, then discard two cards.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

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.

Arcbond

Choose target creature. Whenever that creature is dealt damage this turn, it deals that much damage to each other creature and each player.

Play with Fire

Play with Fire deals 2 damage to any target. If a player is dealt damage this way, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Koth, Fire of Resistance

+2: Search your library for a basic Mountain card, reveal it, put it into your hand, then shuffle.
−3: Koth, Fire of Resistance deals damage to target creature equal to the number of Mountains you control.
−7: You get an emblem with "Whenever a Mountain you control enters, this emblem deals 4 damage to any target."

Vigilante Justice

Whenever a Human you control enters, Vigilante Justice deals 1 damage to any target.

Reinforced Ronin

Haste
At the beginning of your end step, return Reinforced Ronin to its owner's hand.
Channel — {1}{R}, Discard Reinforced Ronin: Draw a card.

Mountain

Pandemonium

Whenever a creature enters, that creature's controller may have it deal damage equal to its power to any target of their choice.