Coat of Arms

Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)

Dragonspeaker Shaman

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

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Karplusan Forest

{T}: Add {C}.
{T}: Add {R} or {G}. Karplusan Forest deals 1 damage to you.

Atarka, World Render

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

Dragonlord's Servant

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

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.

Copperline Gorge

Copperline Gorge enters tapped unless you control two or fewer other lands.
{T}: Add {R} or {G}.

Dragonborn Champion

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

Mountain

Draconic Roar

As an additional cost to cast this spell, you may reveal a Dragon card from your hand.
Draconic Roar deals 3 damage to target creature. If you revealed a Dragon card or controlled a Dragon as you cast this spell, Draconic Roar deals 3 damage to that creature's controller.

Utvara Hellkite

Flying
Whenever a Dragon you control attacks, create a 6/6 red Dragon creature token with flying.