Cone of Flame

Cone of Flame deals 1 damage to any target, 2 damage to another target, and 3 damage to a third target.

Blooming Blast

Gift a Treasure (You may promise an opponent a gift as you cast this spell. If you do, they create a Treasure token before its other effects. It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Blooming Blast deals 2 damage to target creature. If the gift was promised, Blooming Blast also deals 3 damage to that creature's controller.

Collective Defiance

Escalate {1} (Pay this cost for each mode chosen beyond the first.)
Choose one or more —
• Target player discards all the cards in their hand, then draws that many cards.
• Collective Defiance deals 4 damage to target creature.
• Collective Defiance deals 3 damage to target opponent or planeswalker.

Barbed Lightning

Choose one —
• Barbed Lightning deals 3 damage to target creature.
• Barbed Lightning deals 3 damage to target player or planeswalker.
Entwine {2} (Choose both if you pay the entwine cost.)

Carbonize

Carbonize deals 3 damage to any target. If it's a creature, it can't be regenerated this turn, and if it would die this turn, exile it instead.

Bring Low

Bring Low deals 3 damage to target creature. If that creature has a +1/+1 counter on it, Bring Low deals 5 damage to it instead.

Blood Oath

Choose a card type. Target opponent reveals their hand. Blood Oath deals 3 damage to that player for each card of the chosen type revealed this way. (Artifact, battle, creature, enchantment, instant, kindred, land, planeswalker, and sorcery are card types.)

Brimstone Volley

Brimstone Volley deals 3 damage to any target.
Morbid — Brimstone Volley deals 5 damage instead if a creature died this turn.

Blasphemous Act

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

Cackling Flames

Cackling Flames deals 3 damage to any target.
Hellbent — Cackling Flames deals 5 damage instead if you have no cards in hand.

Brotherhood's End

Choose one —
• Brotherhood's End deals 3 damage to each creature and each planeswalker.
• Destroy all artifacts with mana value 3 or less.

Call In a Professional

Players can't gain life this turn. Damage can't be prevented this turn. Call In a Professional deals 3 damage to any target. (Shield counters don't prevent this damage as they're removed.)

Annihilating Fire

Annihilating Fire deals 3 damage to any target. If a creature dealt damage this way would die this turn, exile it instead.

Killer

Killer deals 3 damage to target creature and each other creature that shares a creature type with it.

Coward

Target creature can't block this turn and becomes a Coward in addition to its other types until end of turn.
Time travel.

Coward // Killer

Abrade

Choose one —
• Abrade deals 3 damage to target creature.
• Destroy target artifact.

Blazing Salvo

Blazing Salvo deals 3 damage to target creature unless that creature's controller has Blazing Salvo deal 5 damage to them.

Anger of the Gods

Anger of the Gods deals 3 damage to each creature. If a creature dealt damage this way would die this turn, exile it instead.

Burn Trail

Burn Trail deals 3 damage to any target.
Conspire (As you cast this spell, you may tap two untapped creatures you control that share a color with it. When you do, copy it and you may choose a new target for the copy.)

Krark, the Thumbless

Whenever you cast an instant or sorcery spell, flip a coin. If you lose the flip, return that spell to its owner's hand. If you win the flip, copy that spell, and you may choose new targets for the copy.
Partner (You can have two commanders if both have partner.)

Cathartic Pyre

Choose one —
• Cathartic Pyre deals 3 damage to target creature or planeswalker.
• Discard up to two cards, then draw that many cards.

Burn the Impure

Burn the Impure deals 3 damage to target creature. If that creature has infect, Burn the Impure deals 3 damage to that creature's controller.

Boltwave

Boltwave deals 3 damage to each opponent.

Arc Lightning

Arc Lightning deals 3 damage divided as you choose among one, two, or three targets.

Bolt of Keranos

Bolt of Keranos deals 3 damage to any target. Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Cryoclasm

Destroy target Plains or Island. Cryoclasm deals 3 damage to that land's controller.