Atarka, World Render

Flying, trample
Whenever a Dragon you control attacks, it gains double strike 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."

Green Dragon

Flying
Poison Breath — When this creature enters, until end of turn, whenever a creature an opponent controls is dealt damage, destroy it.

Maelstrom of the Spirit Dragon

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a Dragon spell or an Omen spell.
{4}, {T}, Sacrifice this land: Search your library for a Dragon card, reveal it, put it into your hand, then shuffle.

Hellkite Punisher

Flying
{R}: This creature gets +1/+0 until end of turn.

Sarkhan, Fireblood

+1: You may discard a card. If you do, draw a card.
+1: Add two mana in any combination of colors. Spend this mana only to cast Dragon spells.
−7: Create four 5/5 red Dragon creature tokens with flying.

Shivan Dragon

Greenweaver Druid

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 this card from your graveyard to your hand.

Ashroot Animist

Trample
Whenever this creature attacks, another target creature you control gains trample and gets +X/+X until end of turn, where X is this creature's power.

Elvish Mystic

Magma Spray

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

Caldera Pyremaw

Flying
Whenever you cast an instant or sorcery spell, put a +1/+1 counter on this creature. Then this creature deals damage equal to its power to target opponent.

Harbinger of the Hunt

Flying
{2}{R}: This creature deals 1 damage to each creature without flying.
{2}{G}: This creature deals 1 damage to each other creature with flying.

Ancient Bronze Dragon

Flying
Whenever this creature deals combat damage to a player, roll a d20. When you do, put X +1/+1 counters on each of up to two target creatures, where X is the result.

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

This creature can't be blocked by creatures with power 3 or less.

Dread Linnorm // Scale Deflection

Forest

Cavern-Hoard Dragon

This spell costs {X} less to cast, where X is the greatest number of artifacts an opponent controls.
Flying, trample, haste
Whenever this creature deals combat damage to a player, you create a Treasure token for each artifact that player controls.

Ganax, Astral Hunter

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

Elfhame Druid

{T}: Add {G}.
{T}: Add {G}{G}. Spend this mana only to cast kicked spells.

Mountain

Seismic Rupture

Seismic Rupture deals 2 damage to each creature without flying.

Dragon's Fire

As an additional cost to cast this spell, you may reveal a Dragon card from your hand or choose a Dragon you control.
Dragon's Fire deals 3 damage to target creature or planeswalker. If you revealed a Dragon card or chose a Dragon as you cast this spell, Dragon's Fire deals damage equal to the power of that card or creature instead.

Furyborn Hellkite

Bloodthirst 6 (If an opponent was dealt damage this turn, this creature enters with six +1/+1 counters on it.)
Flying

Thrill of Possibility

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

Scaled Nurturer

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

Gilanra, Caller of Wirewood

{T}: Add {G}. When you spend this mana to cast a spell with mana value 6 or greater, draw a card.
Partner (You can have two commanders if both have partner.)

Dragonlord Atarka

Flying, trample
When Dragonlord Atarka enters, it deals 5 damage divided as you choose among any number of target creatures and/or planeswalkers your opponents control.

Hellkite Charger

Flying, haste
Whenever this creature attacks, you may pay {5}{R}{R}. If you do, untap all attacking creatures and after this phase, there is an additional combat phase.

Destructor Dragon

Flying
When this creature dies, destroy target noncreature permanent.

Crash Through

Creatures you control gain trample until end of turn. (Each of those creature can deal excess combat damage to the player or planeswalker it's attacking.)
Draw a card.

Draconic Muralists

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

Dragonspeaker Shaman

Dragon spells you cast cost {2} less to cast.

Chaos Dragon

Flying, haste
This creature attacks each combat if able.
At the beginning of combat on your turn, each player rolls a d20. If one or more opponents had the highest result, this creature can't attack those players or planeswalkers they control this combat.

Shivan Fire

Kicker {4} (You may pay an additional {4} as you cast this spell.)
Shivan Fire deals 2 damage to target creature. If this spell was kicked, it deals 4 damage instead.

Dragonborn Champion

Trample
Whenever a source you control deals 5 or more damage to a player, draw a card.