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.

Ramunap Ruins

{T}: Add {C}.
{T}, Pay 1 life: Add {R}.
{2}{R}{R}, {T}, Sacrifice a Desert: Ramunap Ruins deals 2 damage to each opponent.

Brash Taunter

Indestructible
Whenever Brash Taunter is dealt damage, it deals that much damage to target opponent.
{2}{R}, {T}: Brash Taunter fights another target creature.

Yidaro, Wandering Monster

Trample, haste
Cycling {1}{R}
When you cycle Yidaro, Wandering Monster, shuffle it into your library from your graveyard. If you've cycled a card named Yidaro, Wandering Monster four or more times this game, put it onto the battlefield from your graveyard instead. (Do this before you draw.)

Chandra, Torch of Defiance

+1: Exile the top card of your library. You may cast that card. If you don't, Chandra, Torch of Defiance deals 2 damage to each opponent.
+1: Add {R}{R}.
−3: Chandra, Torch of Defiance deals 4 damage to target creature.
−7: You get an emblem with "Whenever you cast a spell, this emblem deals 5 damage to any target."

Castle Embereth

Castle Embereth enters tapped unless you control a Mountain.
{T}: Add {R}.
{1}{R}{R}, {T}: Creatures you control get +1/+0 until end of turn.

Nahiri's Wrath

As an additional cost to cast this spell, discard X cards.
Nahiri's Wrath deals damage equal to the total mana value of the discarded cards to each of up to X target creatures and/or planeswalkers.

Abrade

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

Fight with Fire

Kicker {5}{R} (You may pay an additional {5}{R} as you cast this spell.)
Fight with Fire deals 5 damage to target creature. If this spell was kicked, it deals 10 damage divided as you choose among any number of targets instead. (Those targets can include players and planeswalkers.)

Sundering Stroke

Sundering Stroke deals 7 damage divided as you choose among one, two, or three targets. If at least seven red mana was spent to cast this spell, instead Sundering Stroke deals 7 damage to each of those permanents and/or players.

Drakuseth, Maw of Flames

Flying
Whenever Drakuseth attacks, it deals 4 damage to any target and 3 damage to each of up to two other targets.

Irencrag Feat

Add seven {R}. You can cast only one more spell this turn.

Boros Reckoner

Whenever Boros Reckoner is dealt damage, it deals that much damage to any target.
{R/W}: Boros Reckoner gains first strike until end of turn.

Combustible Gearhulk

First strike
When Combustible Gearhulk enters, target opponent may have you draw three cards. If the player doesn't, you mill three cards, then Combustible Gearhulk deals damage to that player equal to the total mana value of those cards.

Star of Extinction

Destroy target land. Star of Extinction deals 20 damage to each creature and each planeswalker.

Lava Coil

Lava Coil deals 4 damage to target creature. If that creature would die this turn, exile it instead.

Mountain

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.