Fumiko the Lowblood

Fumiko the Lowblood has bushido X, where X is the number of attacking creatures. (Whenever this creature blocks or becomes blocked, it gets +X/+X until end of turn.)
Creatures your opponents control attack each combat if able.

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.

Unruly Catapult

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

Furious Reprisal

Furious Reprisal deals 2 damage to each of two targets.

Scorchwalker

Bloodrush — {1}{R}{R}, Discard Scorchwalker: Target attacking creature gets +5/+1 until end of turn.

Lightning-Rig Crew

{T}: Lightning-Rig Crew deals 1 damage to each opponent.
Whenever you cast a Pirate spell, untap Lightning-Rig Crew.

Madcap Skills

Enchant creature
Enchanted creature gets +3/+0 and has menace.

Kessig Flamebreather

Whenever you cast a noncreature spell, Kessig Flamebreather deals 1 damage to each opponent.

Scab-Clan Berserker

Haste
Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever an opponent casts a noncreature spell, if Scab-Clan Berserker is renowned, Scab-Clan Berserker deals 2 damage to that player.

Grapeshot

Grapeshot deals 1 damage to any target.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Guttersnipe

Whenever you cast an instant or sorcery spell, Guttersnipe deals 2 damage to each opponent.

Last Chance

Take an extra turn after this one. At the beginning of that turn's end step, you lose the game.

Rush of Blood

Target creature gets +X/+0 until end of turn, where X is its power.

Magma Spray

Magma Spray deals 2 damage to target creature. If that creature would die this turn, exile it instead.

Solphim, Mayhem Dominus

If a source you control would deal noncombat damage to an opponent or a permanent an opponent controls, it deals double that damage to that player or permanent instead.
{1}{R/P}{R/P}, Discard two cards: Put an indestructible counter on Solphim, Mayhem Dominus. ({R/P} can be paid with either {R} or 2 life.)

Electrostatic Field

Defender
Whenever you cast an instant or sorcery spell, Electrostatic Field deals 1 damage to each opponent.

Sol Ring

Boiling Earth

Boiling Earth deals 1 damage to each creature your opponents control.
Awaken 4—{6}{R} (If you cast this spell for {6}{R}, also put four +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

Defiler of Instinct

First strike
As an additional cost to cast red permanent spells, you may pay 2 life. Those spells cost {R} less to cast if you paid life this way. This effect reduces only the amount of red mana you pay.
Whenever you cast a red permanent spell, Defiler of Instinct deals 1 damage to any target.

Rise to the Challenge

Target creature gets +2/+0 and gains first strike until end of turn.

Chandra's Magmutt

{T}: Chandra's Magmutt deals 1 damage to target player or planeswalker.

Chandra's Pyrohelix

Chandra's Pyrohelix deals 2 damage divided as you choose among one or two targets.

Imodane, the Pyrohammer

Whenever an instant or sorcery spell you control that targets only a single creature deals damage to that creature, Imodane deals that much damage to each opponent.

Thrill of Possibility

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

Witty Roastmaster

Alliance — Whenever another creature enters the battlefield under your control, Witty Roastmaster deals 1 damage to each opponent.

Electrickery

Electrickery deals 1 damage to target creature you don't control.
Overload {1}{R} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Tibalt, Rakish Instigator

Your opponents can't gain life.
−2: Create a 1/1 red Devil creature token with "When this creature dies, it deals 1 damage to any target."

Firebrand Archer

Whenever you cast a noncreature spell, Firebrand Archer deals 1 damage to each opponent.

Unleash Fury

Double the power of target creature until end of turn.

Dragon Mantle

Enchant creature
When Dragon Mantle enters the battlefield, draw a card.
Enchanted creature has "{R}: This creature gets +1/+0 until end of turn."

Erebor Flamesmith

Whenever you cast an instant or sorcery spell, Erebor Flamesmith deals 1 damage to each opponent.

Mountain

Make Mischief

Make Mischief deals 1 damage to any target. Create a 1/1 red Devil creature token. It has "When this creature dies, it deals 1 damage to any target."

Flick a Coin

Flick a Coin deals 1 damage to any target. You create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Draw a card.

Heartless Hidetsugu

{T}: Heartless Hidetsugu deals damage to each player equal to half that player's life total, rounded down.

Runaway Steam-Kin

Whenever you cast a red spell, if Runaway Steam-Kin has fewer than three +1/+1 counters on it, put a +1/+1 counter on Runaway Steam-Kin.
Remove three +1/+1 counters from Runaway Steam-Kin: Add {R}{R}{R}.

The Great Work

(As this Saga enters and after your draw step, add a lore counter.)
I — The Great Work deals 3 damage to target opponent and each creature they control.
II — Create three Treasure tokens.
III — Until end of turn, you may cast instant and sorcery spells from any graveyard. If a spell cast this way would be put into a graveyard, exile it instead. Exile The Great Work, then return it to the battlefield (front face up).

Urabrask

First strike
Whenever you cast an instant or sorcery spell, Urabrask deals 1 damage to target opponent. Add {R}.
{R}: Exile Urabrask, then return it to the battlefield transformed under its owner's control. Activate only as a sorcery and only if you've cast three or more instant and/or sorcery spells this turn.

Urabrask // The Great Work

Torbran, Thane of Red Fell

If a red source you control would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 2 instead.

Goblin Arsonist

When Goblin Arsonist dies, you may have it deal 1 damage to any target.

Tectonic Hazard

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

Blisterspit Gremlin

{1}, {T}: Blisterspit Gremlin deals 1 damage to each opponent.
Whenever you cast a noncreature spell, untap Blisterspit Gremlin.

Arc Lightning

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

Spireside Infiltrator

Whenever Spireside Infiltrator becomes tapped, it deals 1 damage to each opponent.

Titan's Strength

Target creature gets +3/+1 until end of turn. Scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)

Brimstone Trebuchet

Defender, reach
{T}: Brimstone Trebuchet deals 1 damage to each opponent.
Whenever a Knight enters the battlefield under your control, untap Brimstone Trebuchet.

Chandra, Dressed to Kill

+1: Add {R}. Chandra, Dressed to Kill deals 1 damage to up to one target player or planeswalker.
+1: Exile the top card of your library. If it's red, you may cast it this turn.
−7: Exile the top five cards of your library. You may cast red spells from among them this turn. You get an emblem with "Whenever you cast a red spell, this emblem deals X damage to any target, where X is the amount of mana spent to cast that spell."

Breath Weapon

Breath Weapon deals 2 damage to each non-Dragon creature.

Gut Shot

({R/P} can be paid with either {R} or 2 life.)
Gut Shot deals 1 damage to any target.

Sawblade Scamp

Haste
Whenever you cast a noncreature spell, put an oil counter on Sawblade Scamp.
{T}, Remove an oil counter from Sawblade Scamp: It deals 1 damage to each opponent.

Impact Tremors

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

Blazing Crescendo

Target creature gets +3/+1 until end of turn.
Exile the top card of your library. Until the end of your next turn, you may play that card.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Dual Shot

Dual Shot deals 1 damage to each of up to two target creatures.

Thermo-Alchemist

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

Go-Shintai of Ancient Wars

First strike
At the beginning of your end step, you may pay {1}. When you do, Go-Shintai of Ancient Wars deals X damage to target player or planeswalker, where X is the number of Shrines you control.

Livewire Lash

Equipped creature gets +2/+0 and has "Whenever this creature becomes the target of a spell, this creature deals 2 damage to any target."
Equip {2}

Vindictive Flamestoker

Whenever you cast a noncreature spell, put an oil counter on Vindictive Flamestoker.
{6}{R}, Sacrifice Vindictive Flamestoker: Discard your hand, then draw four cards. This ability costs {1} less to activate for each oil counter on Vindictive Flamestoker.

Fiery Confluence

Choose three. You may choose the same mode more than once.
• Fiery Confluence deals 1 damage to each creature.
• Fiery Confluence deals 2 damage to each opponent.
• Destroy target artifact.

Temple of Power

(Transforms from Ojer Axonil, Deepest Might.)
{T}: Add {R}.
{2}{R}, {T}: Transform Temple of Power. Activate only if red sources you controlled dealt 4 or more noncombat damage this turn and only as a sorcery.

Ojer Axonil, Deepest Might

Trample
If a red source you control would deal an amount of noncombat damage less than Ojer Axonil's power to an opponent, that source deals damage equal to Ojer Axonil's power instead.
When Ojer Axonil dies, return it to the battlefield tapped and transformed under its owner's control.

Ojer Axonil, Deepest Might // Temple of Power

Chandra's Incinerator

This spell costs {X} less to cast, where X is the total amount of noncombat damage dealt to your opponents this turn.
Trample
Whenever a source you control deals noncombat damage to an opponent, Chandra's Incinerator deals that much damage to target creature or planeswalker that player controls.

Furious Resistance

Target blocking creature gets +3/+0 and gains first strike until end of turn.

Skinbrand Goblin

Bloodrush — {R}, Discard Skinbrand Goblin: Target attacking creature gets +2/+1 until end of turn.

Manabarbs

Whenever a player taps a land for mana, Manabarbs deals 1 damage to that player.