Mountain

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."

Rapacious Dragon

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

Dragonlord's Servant

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

Reckless Barbarian

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

Seething Song

Breath Weapon

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

Draconic Lore

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

Bathe in Gold

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

Young Red Dragon

Young Red Dragon // Bathe in Gold

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

Carnelian Orb of Dragonkind

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

Swiftwater Cliffs

Swiftwater Cliffs enters the battlefield tapped.
When Swiftwater Cliffs enters the battlefield, you gain 1 life.
{T}: Add {U} or {R}.

Dragonborn Looter

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

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 of your library and the rest on top in any order.)

Island

Sparktongue Dragon

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