Blade of Selves

Equipped creature has myriad. (Whenever it attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)
Equip {4}

Miirym, Sentinel Wyrm

Flying, ward {2}
Whenever another nontoken Dragon you control enters, create a token that's a copy of it, except the token isn't legendary.

Lozhan, Dragons' Legacy

Flying
Whenever you cast an Adventure or Dragon spell, Lozhan, Dragons' Legacy deals damage equal to that spell's mana value to any target that isn't a commander.

Atarka, World Render

Flying, trample
Whenever a Dragon you control attacks, it gains double strike until end of turn.

Scaled Nurturer

{T}: Add {G}. When you spend this mana to cast a Dragon creature spell, you gain 2 life.

Thrakkus the Butcher

Trample
Whenever Thrakkus the Butcher attacks, double the power of each Dragon you control until end of turn.

Bane's Contingency

Counter target spell. If that spell targets a commander you control, instead counter that spell, scry 2, then draw a card.

Dragon's Hoard

Whenever a Dragon you control enters, put a gold counter on Dragon's Hoard.
{T}, Remove a gold counter from Dragon's Hoard: Draw a card.
{T}: Add one mana of any color.

Island

Korlessa, Scale Singer

You may look at the top card of your library any time.
You may cast Dragon spells from the top of your library.

Carnelian Orb of Dragonkind

{T}: Add {R}. If that mana is spent on a Dragon creature spell, it gains haste until end of turn.

Acolyte of Bahamut

Commander creatures you own have "The first Dragon spell you cast each turn costs {2} less to cast."

Nature's Lore

Search your library for a Forest card, put that card onto the battlefield, then shuffle.

Skanos Dragonheart

Whenever Skanos Dragonheart attacks, it gets +X/+X until end of turn, where X is the greatest power among other Dragons you control and Dragon cards in your graveyard.
Choose a Background (You can have a Background as a second commander.)

You Meet in a Tavern

Choose one —
• Form a Party — Look at the top five cards of your library. You may reveal any number of creature cards from among them and put them into your hand. Put the rest on the bottom of your library in a random order.
• Start a Brawl — Creatures you control get +2/+2 until end of turn.

Sky Diamond

Draconic Muralists

When Draconic Muralists dies, you may search your library for a Dragon card, reveal it, put it into your hand, then shuffle.

Forest

Poison the Blade

Target creature gains deathtouch until end of turn.
Draw a card.

Stirring Bard

Defender
When Stirring Bard enters, you take the initiative.
Mantle of Inspiration — {T}: Target creature gains menace and haste until end of turn.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Tiamat's Fanatics

Haste
Myriad (Whenever this creature attacks, for each opponent other than defending player, you may create a token copy that's tapped and attacking that player or a planeswalker they control. Exile the tokens at end of combat.)

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.

Draconic Lore

This spell costs {2} less to cast if you control a Dragon.
Draw three cards.

Owlbear Shepherd

At the beginning of your end step, if creatures you control have total power 8 or greater, draw a card.

Stunning Strike

Flash
Enchant creature
When Stunning Strike enters, tap enchanted creature and remove it from combat.
As long as enchanted creature isn't legendary, it doesn't untap during its controller's untap step.

Sand Augury

Scry 1, then draw a card. (Then exile this card. You may cast the creature later from exile.)

Young Blue Dragon

Young Blue Dragon // Sand Augury

Reflecting Pool

{T}: Add one mana of any type that a land you control could produce.

Oceanus Dragon

Flying
When Oceanus Dragon enters, tap target creature an opponent controls. Goad it. (Until your next turn, that creature attacks each combat if able and attacks a player other than you if able.)

Avenging Hunter

Trample
When Avenging Hunter enters, you take the initiative.

Swashbuckler Extraordinaire

When Swashbuckler Extraordinaire enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Whenever you attack, you may sacrifice one or more Treasures. When you do, up to that many target creatures gain double strike until end of turn.

Lurking Green Dragon

Flying
Lurking Green Dragon can't attack unless defending player controls a creature with flying.

Wrathful Red Dragon

Flying
Whenever a Dragon you control is dealt damage, it deals that much damage to any target that isn't a Dragon.

Renari, Merchant of Marvels

You may cast Dragon spells and artifact spells as though they had flash.
Choose a Background (You can have a Background as a second commander.)

Earthquake Dragon

This spell costs {X} less to cast, where X is the total mana value of Dragons you control.
Flying, trample
{2}{G}, Sacrifice a land: Return Earthquake Dragon from your graveyard to your hand.

Spire Garden

Spire Garden enters tapped unless you have two or more opponents.
{T}: Add {R} or {G}.

Explosive Crystal

Explosive Crystal deals 4 damage divided as you choose among any number of targets. (Then exile this card. You may cast the creature later from exile.)

Amethyst Dragon

Amethyst Dragon // Explosive Crystal

Shiny Impetus

Enchant creature
Enchanted creature gets +2/+2 and is goaded. (It attacks each combat if able and attacks a player other than you if able.)
Whenever enchanted creature attacks, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Predatory Impetus

Enchant creature
Enchanted creature gets +3/+3, must be blocked if able, and is goaded. (It attacks each combat if able and attacks a player other than you if able.)

Ancient Silver Dragon

Flying
Whenever Ancient Silver Dragon deals combat damage to a player, roll a d20. Draw cards equal to the result. You have no maximum hand size for the rest of the game.

Chardalyn Dragon

Dissonant Wave

Counter target activated or triggered ability from a noncreature source. (Then exile this card. You may cast the creature later from exile.)

Emerald Dragon

Emerald Dragon // Dissonant Wave

Ganax, Astral Hunter

Flying
Whenever Ganax, Astral Hunter or another Dragon you control enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Choose a Background (You can have a Background as a second commander.)

Jade Orb of Dragonkind

{T}: Add {G}. When you spend this mana to cast a Dragon creature spell, it enters with an additional +1/+1 counter on it and gains hexproof until your next turn. (It can't be the target of spells or abilities your opponents control.)

Ambitious Dragonborn

Ambitious Dragonborn enters with X +1/+1 counters on it, where X is the greatest power among creatures you control and creature cards in your graveyard.

Breath Weapon

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

Lapis Orb of Dragonkind

{T}: Add {U}. When you spend this mana to cast a Dragon creature spell, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Scale Deflection

Put two +1/+1 counters on target creature and untap it. It gains hexproof until end of turn. (Then exile this card. You may cast the creature later from exile.)

Dread Linnorm

Dread Linnorm can't be blocked by creatures with power 3 or less.

Dread Linnorm // Scale Deflection

Capsizing Wave

Return target creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

Sword Coast Serpent

Sword Coast Serpent can't be blocked as long as you've cast a noncreature spell this turn.

Sword Coast Serpent // Capsizing Wave

Band Together

Up to two target creatures you control each deal damage equal to their power to another target creature.

Fire Diamond

Fire Diamond enters tapped.
{T}: Add {R}.

Overwhelming Encounter

Creatures you control gain vigilance and trample until end of turn. Roll a d20.
1—9 | Creatures you control get +2/+2 until end of turn.
10—19 | Put two +1/+1 counters on each creature you control.
20 | Put four +1/+1 counters on each creature you control.

Psionic Pulse

Counter target noncreature spell. (Then exile this card. You may cast the creature later from exile.)

Sapphire Dragon

Flying
Whenever Sapphire Dragon attacks or blocks, scry 2.

Sapphire Dragon // Psionic Pulse

Mountain

Bathe in Gold

Create a Treasure token. (Then exile this card. You may cast the creature later from exile.)