Herigast, Erupting Nullkite

Emerge {6}{R}{R} (You may cast this spell by sacrificing a creature and paying the emerge cost reduced by that creature's mana value.)
When you cast this spell, you may exile your hand. If you do, draw three cards.
Flying
Each creature spell you cast has emerge. The emerge cost is equal to its mana cost.

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.

Avenging Hunter

Trample
When Avenging Hunter enters, you take the initiative.

Stingerback Terror

Flying, trample
Stingerback Terror gets -1/-1 for each card in your hand.
Plot {2}{R} (You may pay {2}{R} and exile this card from your hand. Cast it as a sorcery on a later turn without paying its mana cost. Plot only as a sorcery.)

Shivan Branch-Burner

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Flying, haste

Thrakkus the Butcher

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

Lurking Green Dragon

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

Dragonborn Looter

{1}, {T}: Draw a card, then discard a card.

Rapacious Dragon

Flying
When this creature enters, create two Treasure tokens. (They're artifacts with "{T}, Sacrifice this token: Add one mana of any color.")

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

Silvanus's Invoker

Conjure Elemental — {8}: Untap target land you control. It becomes an 8/8 Elemental creature with trample and haste until end of turn. It's still a land.

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

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

Scion of Draco

Domain — This spell costs {2} less to cast for each basic land type among lands you control.
Flying
Each creature you control has vigilance if it's white, hexproof if it's blue, lifelink if it's black, first strike if it's red, and trample if it's green.

Scaled Nurturer

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

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.)

Niv-Mizzet, Parun

This spell can't be countered.
Flying
Whenever you draw a card, Niv-Mizzet, Parun deals 1 damage to any target.
Whenever a player casts an instant or sorcery spell, you draw a card.

Realm-Scorcher Hellkite

Bargain (You may sacrifice an artifact, enchantment, or token as you cast this spell.)
Flying, haste
When Realm-Scorcher Hellkite enters, if it was bargained, add four mana in any combination of colors.
{1}{R}: Realm-Scorcher Hellkite deals 1 damage to any target.

Bhaal's Invoker

Scorching Ray — {8}: Bhaal's Invoker deals 4 damage to each opponent.

Steel Hellkite

Flying
{2}: This creature gets +1/+0 until end of turn.
{X}: Destroy each nonland permanent with mana value X whose controller was dealt combat damage by this creature this turn. Activate only once each turn.

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.)

Chardalyn Dragon

Henge Guardian

{2}: Henge Guardian gains trample until end of turn.

Patron of the Arts

When Patron of the Arts enters or dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: 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.)

Pseudodragon Familiar

Flying
{2}{U}: Target creature gains flying until end of turn.

Archive Dragon

Flying
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
When Archive Dragon enters, scry 2.

Reckless Barbarian

Sacrifice Reckless Barbarian: Add {R}{R}.

Fledgling Dragon

Flying
Threshold — As long as seven or more cards are in your graveyard, Fledgling Dragon gets +3/+3 and has "{R}: Fledgling Dragon gets +1/+0 until end of turn."

Nesting Dragon

Flying
Landfall — Whenever a land you control enters, create a 0/2 red Dragon Egg creature token with defender and "When this creature dies, create a 2/2 red Dragon creature token with flying and '{R}: This creature gets +1/+0 until end of turn.'"

Thriving Skyclaw

Flying
When Thriving Skyclaw enters, you get {E}{E}{E} (three energy counters).
Whenever Thriving Skyclaw attacks, you may pay {E}{E}{E}. If you do, put a +1/+1 counter on it.

Hoarding Dragon

Flying
When this creature enters, you may search your library for an artifact card, exile it, then shuffle.
When this creature dies, you may put the exiled card into its owner's hand.

Sparktongue Dragon

Flying
When Sparktongue Dragon enters, you may pay {2}{R}. When you do, it deals 3 damage to any target.