Prisoner's Dilemma

Each opponent secretly chooses silence or snitch, then the choices are revealed. If each opponent chose silence, Prisoner's Dilemma deals 4 damage to each of them. If each opponent chose snitch, Prisoner's Dilemma deals 8 damage to each of them. Otherwise, Prisoner's Dilemma deals 12 damage to each opponent who chose silence.
Flashback {5}{R}{R}

Kessig Flamebreather

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

Devoted Duelist

Haste
Flurry — Whenever you cast your second spell each turn, this creature deals 1 damage to each opponent.

Panicked Altisaur

Reach
{T}: This creature deals 2 damage to each opponent.

Hearthborn Battler

Haste
Whenever a player casts their second spell each turn, this creature deals 2 damage to target opponent.

Rig for War

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

Sabotender

Reach
Landfall — Whenever a land you control enters, this creature deals 1 damage to each opponent.

Dragon Mantle

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

Sol Ring

Cemetery Gatekeeper

First strike
When this creature enters, exile a card from a graveyard.
Whenever a player plays a land or casts a spell, if it shares a card type with the exiled card, this creature deals 2 damage to that player.

Return the Favor

Spree (Choose one or more additional costs.)
+ {1} — Copy target instant spell, sorcery spell, activated ability, or triggered ability. You may choose new targets for the copy.
+ {1} — Change the target of target spell or ability with a single target.

Acidic Soil

Acidic Soil deals damage to each player equal to the number of lands they control.

Cursed Mirror

{T}: Add {R}.
As this artifact enters, you may have it become a copy of any creature on the battlefield until end of turn, except it has haste.

Aettir and Priwen

Equipped creature has base power and toughness X/X, where X is your life total.
Equip {5}

Jeska's Will

Choose one. If you control a commander as you cast this spell, you may choose both instead.
• Add {R} for each card in target opponent's hand.
• Exile the top three cards of your library. You may play them this turn.

Blasphemous Act

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

Twinflame Tyrant

Flying
If a source you control would deal damage to an opponent or a permanent an opponent controls, it deals double that damage instead.

Manabarbs

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

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, this creature deals that much damage to target creature or planeswalker that player controls.

Faithless Looting

Draw two cards, then discard two cards.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

The Fire Crystal

Red spells you cast cost {1} less to cast.
Creatures you control have haste.
{4}{R}{R}, {T}: Create a token that's a copy of target creature you control. Sacrifice it at the beginning of the next end step.

Wrenn's Resolve

Exile the top two cards of your library. Until the end of your next turn, you may play those cards.

Mage Siege

Create a 0/1 black Wizard creature token with "Whenever you cast a noncreature spell, this token deals 1 damage to each opponent."

Lindblum, Industrial Regency

Lindblum, Industrial Regency // Mage Siege

Fire-Rim Form

Flash
Enchant creature
When this Aura enters, enchanted creature gains first strike until end of turn.
Enchanted creature gets +2/+0.

Harsh Mentor

Whenever an opponent activates an ability of an artifact, creature, or land on the battlefield, if it isn't a mana ability, this creature deals 2 damage to that player.

War Room

{T}: Add {C}.
{3}, {T}, Pay life equal to the number of colors in your commanders' color identity: Draw a card.

Impact Tremors

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

Barbarian Ring

{T}: Add {R}. This land deals 1 damage to you.
Threshold — {R}, {T}, Sacrifice this land: It deals 2 damage to any target. Activate only if seven or more cards are in your graveyard.

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

Magmakin Artillerist

Whenever you discard one or more cards, this creature deals that much damage to each opponent.
Cycling {1}{R} ({1}{R}, Discard this card: Draw a card.)
When you cycle this card, it deals 1 damage to each opponent.

The Endstone

Whenever you play a land or cast a spell, draw a card.
At the beginning of your end step, your life total becomes half your starting life total, rounded up.

Wayfarer's Bauble

{2}, {T}, Sacrifice this artifact: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Ashling, Flame Dancer

You don't lose unspent red mana as steps and phases end.
Magecraft — Whenever you cast or copy an instant or sorcery spell, discard a card, then draw a card. If this is the second time this ability has resolved this turn, Ashling deals 2 damage to each opponent and each creature they control. If it's the third time, add {R}{R}{R}{R}.

Shocking Sharpshooter

Reach
Whenever another creature you control enters, this creature deals 1 damage to target opponent.

Hired Claw

Whenever you attack with one or more Lizards, this creature deals 1 damage to target opponent.
{1}{R}: Put a +1/+1 counter on this creature. Activate only if an opponent lost life this turn and only once each turn.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Weftstalker Ardent

Whenever another creature or artifact you control enters, this creature deals 1 damage to each opponent.
Warp {R} (You may cast this card from your hand for its warp cost. Exile this creature at the beginning of the next end step, then you may cast it from exile on a later turn.)

Cursed Recording

Whenever you cast an instant or sorcery spell, put a time counter on this artifact. Then if there are seven or more time counters on it, remove those counters and it deals 20 damage to you.
{T}: When you next cast an instant or sorcery spell this turn, copy that spell. You may choose new targets for the copy.

Mountain

Molten Gatekeeper

Whenever another creature you control enters, this creature deals 1 damage to each opponent.
Unearth {R} ({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.)

Temple of Power

(Transforms from Ojer Axonil, Deepest Might.)
{T}: Add {R}.
{2}{R}, {T}: Transform this land. 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

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 token: Add one mana of any color.")
Draw a card.

Kavaron, Memorial World

This land enters tapped.
{T}: Add {R}.
Station (Tap another creature you control: Put charge counters equal to its power on this Planet. Station only as a sorcery.)
STATION 12+
{1}{R}, {T}, Sacrifice a land: Create a 2/2 colorless Robot artifact creature token, then creatures you control get +1/+0 and gain haste until end of turn.

Caged Sun

As this artifact enters, choose a color.
Creatures you control of the chosen color get +1/+1.
Whenever a land's ability causes you to add one or more mana of the chosen color, add one additional mana of that color.

War Squeak

Enchant creature
When this Aura enters, target creature an opponent controls can't block this turn.
Enchanted creature gets +1/+1 and has haste.

Tavern Brawler

Commander creatures you own have "At the beginning of your upkeep, exile the top card of your library. This creature gets +X/+0 until end of turn, where X is that card's mana value. You may play that card this turn."

Mysidian Elder

When this creature enters, create a 0/1 black Wizard creature token with "Whenever you cast a noncreature spell, this token deals 1 damage to each opponent."

The Great Work

(As this Saga enters and after your draw step, add a lore counter.)
I — This Saga 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 this Saga, 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

Eidolon of the Great Revel

Whenever a player casts a spell with mana value 3 or less, this creature deals 2 damage to that player.

Needle Drop

Needle Drop deals 1 damage to any target that was dealt damage this turn.
Draw a card.

Shattered Yard

At the beginning of your end step, this Room deals 1 damage to each opponent.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Glassworks

When you unlock this door, this Room deals 4 damage to target creature an opponent controls.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Glassworks // Shattered Yard

Count on Luck

At the beginning of your upkeep, exile the top card of your library. You may play that card this turn.

Firebrand Archer

Will of the Jeskai

Choose one. If you control a commander as you cast this spell, you may choose both instead.
• Each player may discard their hand and draw five cards.
• Each instant and sorcery card in your graveyard gains flashback until end of turn. The flashback cost is equal to its mana cost.

Dwarven Blastminer

{2}{R}, {T}: Destroy target nonbasic land.
Morph {R} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Demand Answers

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

Secluded Starforge

{T}: Add {C}.
{2}, {T}, Tap X untapped artifacts you control: Target creature gets +X/+0 until end of turn. Activate only as a sorcery.
{5}, {T}: Create a 2/2 colorless Robot artifact creature token.

Romantic Rendezvous

Valakut Stoneforge

Valakut Awakening

Put any number of cards from your hand on the bottom of your library, then draw that many cards plus one.

Valakut Awakening // Valakut Stoneforge

Witty Roastmaster

Alliance — Whenever another creature you control enters, this creature deals 1 damage to each opponent.

Winter Moon

Players can't untap more than one nonbasic land during their untap steps.

Tectonic Hazard

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

Opera Love Song

Choose one —
• Exile the top two cards of your library. You may play those cards until your next end step.
• One or two target creatures each get +2/+0 until end of turn.

Blisterspit Gremlin

{1}, {T}: This creature deals 1 damage to each opponent.
Whenever you cast a noncreature spell, untap this creature.

Custody Battle

Enchant creature
Enchanted creature has "At the beginning of your upkeep, target opponent gains control of this creature unless you sacrifice a land."

Scytheclaw Raptor

Whenever a player casts a spell, if it's not their turn, this creature deals 4 damage to them.

Pain for All

Enchant creature you control
When this Aura enters, enchanted creature deals damage equal to its power to any other target.
Whenever enchanted creature is dealt damage, it deals that much damage to each opponent.

Fire Magic

Tiered (Choose one additional cost.)
• Fire — {0} — Fire Magic deals 1 damage to each creature.
• Fira — {2} — Fire Magic deals 2 damage to each creature.
• Firaga — {5} — Fire Magic deals 3 damage to each creature.

Fire Diamond

This artifact enters tapped.
{T}: Add {R}.

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.)

Dwarven Ruins

This land enters tapped.
{T}: Add {R}.
{T}, Sacrifice this land: Add {R}{R}.

Sulfuric Vortex

At the beginning of each player's upkeep, this enchantment deals 2 damage to that player.
If a player would gain life, that player gains no life instead.

Harnfel, Horn of Bounty

Discard a card: Exile the top two cards of your library. You may play those cards this turn.

Birgi, God of Storytelling

Whenever you cast a spell, add {R}. Until end of turn, you don't lose this mana as steps and phases end.
Creatures you control can boast twice during each of your turns rather than once.

Birgi, God of Storytelling // Harnfel, Horn of Bounty

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.

End the Festivities

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

Razorkin Needlehead

This creature has first strike during your turn.
Whenever an opponent draws a card, this creature deals 1 damage to them.

Tarrian's Soulcleaver

Equipped creature has vigilance.
Whenever another artifact or creature is put into a graveyard from the battlefield, put a +1/+1 counter on equipped creature.
Equip {2}

Purphoros, God of the Forge

Indestructible
As long as your devotion to red is less than five, Purphoros isn't a creature.
Whenever another creature you control enters, Purphoros deals 2 damage to each opponent.
{2}{R}: Creatures you control get +1/+0 until end of turn.

Bolt Bend

This spell costs {3} less to cast if you control a creature with power 4 or greater.
Change the target of target spell or ability with a single target.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice this artifact: Draw a card.

Boltwave

Boltwave deals 3 damage to each opponent.

Shadow of the Goblin

Unreliable Visions — At the beginning of your first main phase, discard a card. If you do, draw a card.
Undying Vengeance — Whenever you play a land or cast a spell from anywhere other than your hand, this enchantment deals 1 damage to each opponent.

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Gleeful Arsonist

Whenever an opponent casts a noncreature spell, this creature deals damage equal to its power to that player.
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Playful Shove

Playful Shove deals 1 damage to any target.
Draw a card.

Abrade

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

Unruly Catapult

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

Zenith Festival

Exile the top X cards of your library. You may play them until the end of your next turn.
Harmonize {X}{R}{R} (You may cast this card from your graveyard for its harmonize cost. You may tap a creature you control to reduce that cost by an amount of generic mana equal to its power. Then exile this spell.)

Krenko's Buzzcrusher

Flying, trample
When this creature enters, for each player, destroy up to one nonbasic land that player controls. For each land destroyed this way, its controller may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.

Zookeeper Mechan

{T}: Add {R}.
{6}{R}: Target creature you control gets +4/+0 until end of turn. Activate only as a sorcery.

Spider-Punk

Riot (This creature enters with your choice of a +1/+1 counter or haste.)
Other Spiders you control have riot.
Spells and abilities can't be countered.
Damage can't be prevented.

Shattering Spree

Replicate {R} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Destroy target artifact.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.