Dragonborn Champion

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

Dragonspeaker Shaman

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

Hellkite Charger

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

Atarka, World Render

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

Thrakkus the Butcher

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

Dragonlord Dromoka

This spell can't be countered.
Flying, lifelink
Your opponents can't cast spells during your turn.

Lathliss, Dragon Queen

Flying
Whenever another nontoken Dragon you control enters, create a 5/5 red Dragon creature token with flying.
{1}{R}: Dragons you control get +1/+0 until end of turn.

Farseek

Search your library for a Plains, Island, Swamp, or Mountain card, put it onto the battlefield tapped, then shuffle.

Scourge of Valkas

Flying
Whenever Scourge of Valkas or another Dragon you control enters, it deals X damage to any target, where X is the number of Dragons you control.
{R}: Scourge of Valkas gets +1/+0 until end of turn.

Dragonmaster Outcast

At the beginning of your upkeep, if you control six or more lands, create a 5/5 red Dragon creature token with flying.

Orb of Dragonkind

{1}, {T}: Add two mana in any combination of colors. Spend this mana only to cast Dragon spells or activate abilities of Dragons.
{R}, {T}, Sacrifice Orb of Dragonkind: Look at the top seven cards of your library. You may reveal a Dragon card from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

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.

Silumgar, the Drifting Death

Flying, hexproof
Whenever a Dragon you control attacks, creatures defending player controls get -1/-1 until end of turn.

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.)

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.

Bladewing the Risen

Flying
When Bladewing the Risen enters, you may return target Dragon permanent card from your graveyard to the battlefield.
{B}{R}: Dragon creatures get +1/+1 until end of turn.

Two-Headed Hellkite

Flying, menace, haste
Whenever Two-Headed Hellkite attacks, draw two cards.

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.

Dragonlord's Servant

Dragon spells you cast cost {1} less to cast.

Rivaz of the Claw

Menace
{T}: Add two mana in any combination of colors. Spend this mana only to cast Dragon creature spells.
Once during each of your turns, you may cast a Dragon creature spell from your graveyard.
Whenever you cast a Dragon creature spell from your graveyard, it gains "When this creature dies, exile it."

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.

Klauth, Unrivaled Ancient

Flying, haste
Whenever Klauth, Unrivaled Ancient attacks, add X mana in any combination of colors, where X is the total power of attacking creatures. Spend this mana only to cast spells. Until end of turn, you don't lose this mana as steps and phases end.

Tiamat

Flying
When Tiamat enters, if you cast it, search your library for up to five Dragon cards not named Tiamat that each have different names, reveal them, put them into your hand, then shuffle.