Banefire

Banefire deals X damage to any target.
If X is 5 or more, this spell can't be countered and the damage can't be prevented.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Quest for Pure Flame

Whenever a source you control deals damage to an opponent, you may put a quest counter on Quest for Pure Flame.
Remove four quest counters from Quest for Pure Flame and sacrifice it: If any source you control would deal damage to a permanent or player this turn, it deals double that damage to that permanent or player instead.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Ideas Unbound

Draw three cards. Discard three cards at the beginning of the next end step.

Scorch Spitter

Whenever Scorch Spitter attacks, it deals 1 damage to the player or planeswalker it's attacking.

Fireball

This spell costs {1} more to cast for each target beyond the first.
Fireball deals X damage divided evenly, rounded down, among any number of targets.

Curiosity

Enchant creature
Whenever enchanted creature deals damage to an opponent, you may draw a card.

Frostboil Snarl

As Frostboil Snarl enters, you may reveal an Island or Mountain card from your hand. If you don't, Frostboil Snarl enters tapped.
{T}: Add {U} or {R}.

Tectonic Hazard

Tectonic Hazard deals 1 damage to each opponent and each creature they control.

Thermo-Alchemist

Defender
{T}: Thermo-Alchemist deals 1 damage to each opponent.
Whenever you cast an instant or sorcery spell, untap Thermo-Alchemist.

Rite of Flame

Add {R}{R}, then add {R} for each card named Rite of Flame in each graveyard.

Simian Spirit Guide

Exile Simian Spirit Guide from your hand: Add {R}.

Island

Firebrand Archer

Whenever you cast a noncreature spell, this creature deals 1 damage to each opponent.

Sigil of Sleep

Enchant creature
Whenever enchanted creature deals damage to a player, return target creature that player controls to its owner's hand.