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.

Phyrexian Dragon Engine

Double strike
When Phyrexian Dragon Engine enters from your graveyard, you may discard your hand. If you do, draw three cards.
Unearth {3}{R}{R}
(Melds with Mishra, Claimed by Gix.)

Broodmate Tyrant

Flying
When Broodmate Tyrant enters, create a 5/5 red Dragon creature token with flying.
Encore {5}{B}{R}{G}

Scaled Nurturer

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

Broodmate Dragon

Flying
When Broodmate Dragon enters, create a 4/4 red Dragon creature token with flying.

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.

Sprite Dragon

Flying, haste
Whenever you cast a noncreature spell, put a +1/+1 counter on Sprite Dragon.

Gond Gate

Gates you control enter untapped.
{T}: Add {C}.
{T}: Add one mana of any color that a Gate you control could produce.

O-Kagachi, Vengeful Kami

Flying, trample
Whenever O-Kagachi, Vengeful Kami deals combat damage to a player, if that player attacked you during their last turn, exile target nonland permanent that player controls.

Shivan Devastator

Flying, haste
Shivan Devastator enters with X +1/+1 counters on it.

Dragonborn Looter

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

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.

Dragon Egg

Defender
When Dragon Egg dies, create a 2/2 red Dragon creature token with flying and "{R}: This creature gets +1/+0 until end of turn."

Scion of the Ur-Dragon

Flying
{2}: Search your library for a Dragon permanent card and put it into your graveyard. If you do, Scion of the Ur-Dragon becomes a copy of that card until end of turn. Then shuffle.

The Ur-Dragon

Eminence — As long as The Ur-Dragon is in the command zone or on the battlefield, other Dragon spells you cast cost {1} less to cast.
Flying
Whenever one or more Dragons you control attack, draw that many cards, then you may put a permanent card from your hand onto the battlefield.

Morophon, the Boundless

Changeling (This card is every creature type.)
As Morophon, the Boundless enters, choose a creature type.
Spells of the chosen type you cast cost {W}{U}{B}{R}{G} less to cast. This effect reduces only the amount of colored mana you pay.
Other creatures you control of the chosen type get +1/+1.

Two-Headed Hellkite

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

Chaos Dragon

Flying, haste
Chaos Dragon 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, Chaos Dragon can't attack those players or planeswalkers they control this combat.

Baldur's Gate

{T}: Add {C}.
{2}, {T}: Add X mana of any one color, where X is the number of other Gates you control.

Dragon Turtle

Flash
Drag Below — When Dragon Turtle enters, tap it and up to one target creature an opponent controls. They don't untap during their controllers' next untap steps.

Atarka, World Render

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

Slumbering Dragon

Flying
Slumbering Dragon can't attack or block unless it has five or more +1/+1 counters on it.
Whenever a creature attacks you or a planeswalker you control, put a +1/+1 counter on Slumbering Dragon.