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.

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Vulshok Sorcerer

Haste
{T}: Vulshok Sorcerer deals 1 damage to any target.

Repercussion

Whenever a creature is dealt damage, Repercussion deals that much damage to that creature's controller.

Jaya, Venerated Firemage

If another red source you control would deal damage to a permanent or player, it deals that much damage plus 1 to that permanent or player instead.
−2: Jaya, Venerated Firemage deals 2 damage to any target.

Thought Vessel

You have no maximum hand size.
{T}: Add {C}.

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.

Plains

Chain of Plasma

Chain of Plasma deals 3 damage to any target. Then that player or that permanent's controller may discard a card. If the player does, they may copy this spell and may choose a new target for that copy.

Smoke Spirits' Aid

For each of up to X target creatures, create a red Aura enchantment token named Smoke Blessing attached to that creature. Those tokens have enchant creature and "When enchanted creature dies, it deals 1 damage to its controller and you create a Treasure token."

Open the Armory

Search your library for an Aura or Equipment card, reveal it, put it into your hand, then shuffle.

Embereth Blaze

Embereth Blaze deals 2 damage to any target. (Then exile this card. You may cast the enchantment later from exile.)

Virtue of Courage

Whenever a source you control deals noncombat damage to an opponent, you may exile that many cards from the top of your library. You may play those cards this turn.

Virtue of Courage // Embereth Blaze

Howlpack Avenger

Whenever a permanent you control is dealt damage, Howlpack Avenger deals that much damage to any target.
{1}{R}: Howlpack Avenger gets +2/+0 until end of turn.
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Ill-Tempered Loner

Whenever Ill-Tempered Loner is dealt damage, it deals that much damage to any target.
{1}{R}: Ill-Tempered Loner gets +2/+0 until end of turn.
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Ill-Tempered Loner // Howlpack Avenger

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Blasphemous Act

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

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.

Goblin Sharpshooter

Goblin Sharpshooter doesn't untap during your untap step.
Whenever a creature dies, untap Goblin Sharpshooter.
{T}: Goblin Sharpshooter deals 1 damage to any target.

End the Festivities

End the Festivities deals 1 damage to each opponent and each creature and planeswalker they control.

Guilty Conscience

Enchant creature
Whenever enchanted creature deals damage, Guilty Conscience deals that much damage to that creature.

Cunning Sparkmage

Haste
{T}: Cunning Sparkmage deals 1 damage to any target.

Mana Geyser

Add {R} for each tapped land your opponents control.

Take Up the Shield

Put a +1/+1 counter on target creature. It gains lifelink and indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Darksteel Myr

Indestructible (Damage and effects that say "destroy" don't destroy this creature. If its toughness is 0 or less, it's still put into its owner's graveyard.)

Boros Charm

Choose one —
• Boros Charm deals 4 damage to target player or planeswalker.
• Permanents you control gain indestructible until end of turn.
• Target creature gains double strike until end of turn.

Flawless Maneuver

If you control a commander, you may cast this spell without paying its mana cost.
Creatures you control gain indestructible until end of turn.

Illusionist's Bracers

Whenever an ability of equipped creature is activated, if it isn't a mana ability, copy that ability. You may choose new targets for the copy.
Equip {3}

Taii Wakeen, Perfect Shot

Whenever a source you control deals noncombat damage to a creature equal to that creature's toughness, draw a card.
{X}, {T}: If a source you control would deal noncombat damage to a permanent or player this turn, it deals that much damage plus X instead.

Gamble

Search your library for a card, put that card into your hand, discard a card at random, then shuffle.

Solar Blaze

Each creature deals damage to itself equal to its power.

Rebuff the Wicked

Counter target spell that targets a permanent you control.

Jeska, Warrior Adept

First strike, haste
{T}: Jeska, Warrior Adept deals 1 damage to any target.

Mountain

Boros Signet

Blazing Sunsteel

Equipped creature gets +1/+0 for each opponent you have.
Whenever equipped creature is dealt damage, it deals that much damage to any target.
Equip {4}

Pariah

Enchant creature
All damage that would be dealt to you is dealt to enchanted creature instead.

Braid of Fire

Cumulative upkeep—Add {R}. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

Spitemare

Whenever Spitemare is dealt damage, it deals that much damage to any target.

Toralf's Hammer

Equipped creature has "{1}{R}, {T}, Unattach Toralf's Hammer: It deals 3 damage to any target. Return Toralf's Hammer to its owner's hand."
Equipped creature gets +3/+0 as long as it's legendary.
Equip {1}{R}

Toralf, God of Fury

Trample
Whenever a creature or planeswalker an opponent controls is dealt excess noncombat damage, Toralf deals damage equal to the excess to any target other than that permanent.

Toralf, God of Fury // Toralf's Hammer

Feather, the Redeemed

Flying
Whenever you cast an instant or sorcery spell that targets a creature you control, exile that card instead of putting it into your graveyard as it resolves. If you do, return it to your hand at the beginning of the next end step.

Darksteel Plate

Indestructible
Equipped creature has indestructible.
Equip {2}

Selfless Savior

Sacrifice Selfless Savior: Another target creature you control gains indestructible until end of turn. (Damage and effects that say "destroy" don't destroy it.)

Acorn Catapult

{1}, {T}: Acorn Catapult deals 1 damage to any target. That permanent's controller or that player creates a 1/1 green Squirrel creature token.

Forbidden Orchard

{T}: Add one mana of any color.
Whenever you tap Forbidden Orchard for mana, target opponent creates a 1/1 colorless Spirit creature token.

Sol Ring

Darksteel Mutation

Enchant creature
Enchanted creature is an Insect artifact creature with base power and toughness 0/1 and has indestructible, and it loses all other abilities, card types, and creature types.

Delayed Blast Fireball

Delayed Blast Fireball deals 2 damage to each opponent and each creature they control. If this spell was cast from exile, it deals 5 damage to each opponent and each creature they control instead.
Foretell {4}{R}{R} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

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.

Arcbond

Choose target creature. Whenever that creature is dealt damage this turn, it deals that much damage to each other creature and each player.

Fighter Class

(Gain the next level as a sorcery to add its ability.)
When Fighter Class enters, search your library for an Equipment card, reveal it, put it into your hand, then shuffle.
{1}{R}{W}: Level 2
Equip abilities you activate cost {2} less to activate.
{3}{R}{W}: Level 3
Whenever a creature you control attacks, up to one target creature blocks it this combat if able.

Lapse of Certainty

Counter target spell. If that spell is countered this way, put it on top of its owner's library instead of into that player's graveyard.

Star of Extinction

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

Gut Shot

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

Caltrops

Whenever a creature attacks, Caltrops deals 1 damage to it.

Prodigal Pyromancer

{T}: Prodigal Pyromancer deals 1 damage to any target.

Leyline Tyrant

Flying
You don't lose unspent red mana as steps and phases end.
When Leyline Tyrant dies, you may pay any amount of {R}. When you do, it deals that much damage to any target.

Chain Reaction

Chain Reaction deals X damage to each creature, where X is the number of creatures on the battlefield.

Sheltering Light

Target creature gains indestructible until end of turn. Scry 1. (Damage and effects that say "destroy" don't destroy the creature.)

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Fear, Fire, Foes!

Damage can't be prevented this turn. Fear, Fire, Foes! deals X damage to target creature and 1 damage to each other creature with the same controller.

Reprieve

Return target spell to its owner's hand.
Draw a card.

Reliquary Tower

Seething Song

Stuffy Doll

Indestructible
As Stuffy Doll enters, choose a player.
Whenever Stuffy Doll is dealt damage, it deals that much damage to the chosen player.
{T}: Stuffy Doll deals 1 damage to itself.

Rem Karolus, Stalwart Slayer

Flying, haste
If a spell would deal damage to you or another permanent you control, prevent that damage.
If a spell would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 1 instead.

Power of Fire

Enchant creature
Enchanted creature has "{T}: This creature deals 1 damage to any target."

Blacksmith's Skill

Target permanent gains hexproof and indestructible until end of turn. If it's an artifact creature, it gets +2/+2 until end of turn.

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.

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Steelshaper's Gift

Search your library for an Equipment card, reveal that card, put it into your hand, then shuffle.

Enlightened Tutor

Search your library for an artifact or enchantment card, reveal it, then shuffle and put that card on top.

Arcane Signet

Vithian Stinger

{T}: Vithian Stinger deals 1 damage to any target.
Unearth {1}{R} ({1}{R}: Return this card from your graveyard to the battlefield. It gains haste. Exile it at the beginning of the next end step or if it would leave the battlefield. Unearth only as a sorcery.)

Angelfire Ignition

Put two +1/+1 counters on target creature. It gains vigilance, trample, lifelink, indestructible, and haste until end of turn.
Flashback {2}{R}{W} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Chandra, the Firebrand

+1: Chandra, the Firebrand deals 1 damage to any target.
−2: When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.
−6: Chandra, the Firebrand deals 6 damage to each of up to six targets.

Akroan Horse

Defender
When Akroan Horse enters, an opponent gains control of it.
At the beginning of your upkeep, each opponent creates a 1/1 white Soldier creature token.

Pyrohemia

At the beginning of the end step, if no creatures are on the battlefield, sacrifice Pyrohemia.
{R}: Pyrohemia deals 1 damage to each creature and each player.

Loran's Escape

Target artifact or creature gains hexproof and indestructible until end of turn. Scry 1.

Shielded by Faith

Enchant creature
Enchanted creature has indestructible.
Whenever a creature enters, you may attach Shielded by Faith to that creature.