Light Up the Stage

Spectacle {R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Exile the top two cards of your library. Until the end of your next turn, you may play those cards.

Mountain

Ash Zealot

First strike, haste
Whenever a player casts a spell from a graveyard, Ash Zealot deals 3 damage to that player.

Generator Servant

{T}, Sacrifice Generator Servant: Add {C}{C}. If that mana is spent on a creature spell, it gains haste until end of turn. (That creature can attack and {T} as soon as it comes under your control.)

Grim Lavamancer

{R}, {T}, Exile two cards from your graveyard: Grim Lavamancer deals 2 damage to any target.

The Flame of Keld

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Discard your hand.
II — Draw two cards.
III — If a red source you control would deal damage to a permanent or player this turn, it deals that much damage plus 2 to that permanent or player instead.

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."

Dragon's Claw

Whenever a player casts a red spell, you may gain 1 life.

Burning-Tree Emissary

When Burning-Tree Emissary enters the battlefield, add {R}{G}.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Smash to Smithereens

Destroy target artifact. Smash to Smithereens deals 3 damage to that artifact's controller.

Reforge the Soul

Each player discards their hand, then draws seven cards.
Miracle {1}{R} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)

Wild Guess

As an additional cost to cast this spell, discard a card.
Draw two cards.

Alchemist's Vial

When Alchemist's Vial enters the battlefield, draw a card.
{1}, {T}, Sacrifice Alchemist's Vial: Target creature can't attack or block this turn.

Devastating Summons

As an additional cost to cast this spell, sacrifice X lands.
Create two X/X red Elemental creature tokens.

Reckless Bushwhacker

Surge {1}{R} (You may cast this spell for its surge cost if you or a teammate has cast another spell this turn.)
Haste
When Reckless Bushwhacker enters the battlefield, if its surge cost was paid, other creatures you control get +1/+0 and gain haste until end of turn.

Insolent Neonate

Menace (This creature can't be blocked except by two or more creatures.)
Discard a card, Sacrifice Insolent Neonate: Draw a card.

Priest of Urabrask

When Priest of Urabrask enters the battlefield, add {R}{R}{R}.

Claim the Firstborn

Gain control of target creature with mana value 3 or less until end of turn. Untap that creature. It gains haste until end of turn.

Myr Superion

Spend only mana produced by creatures to cast this spell.

Storm Entity

Haste
Storm Entity enters the battlefield with a +1/+1 counter on it for each other spell cast this turn.

Ricochet Trap

If an opponent cast a blue spell this turn, you may pay {R} rather than pay this spell's mana cost.
Change the target of target spell with a single target.

Impact Tremors

Whenever a creature enters the battlefield under your control, Impact Tremors deals 1 damage to each opponent.

Goblin Bushwhacker

Kicker {R} (You may pay an additional {R} as you cast this spell.)
When Goblin Bushwhacker enters the battlefield, if it was kicked, creatures you control get +1/+0 and gain haste until end of turn.

Goldhound

First strike
Menace (This creature can't be blocked except by two or more creatures.)
{T}, Sacrifice Goldhound: Add one mana of any color.