Ancient Copper Dragon

Flying
Whenever Ancient Copper Dragon deals combat damage to a player, roll a d20. You create a number of Treasure tokens equal to the result.

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.

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.

Terror of the Peaks

Flying
Spells your opponents cast that target Terror of the Peaks cost an additional 3 life to cast.
Whenever another creature you control enters, Terror of the Peaks deals damage equal to that creature's power to any target.

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.

Old Gnawbone

Flying
Whenever a creature you control deals combat damage to a player, create that many Treasure tokens.

Utvara Hellkite

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

Balefire Dragon

Flying
Whenever Balefire Dragon deals combat damage to a player, it deals that much damage to each creature that player controls.

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.

Steam Vents

({T}: Add {U} or {R}.)
As Steam Vents enters, you may pay 2 life. If you don't, it enters tapped.

Goldspan Dragon

Flying, haste
Whenever Goldspan Dragon attacks or becomes the target of a spell, create a Treasure token.
Treasures you control have "{T}, Sacrifice this artifact: Add two mana of any one color."