The Ur-Dragon
Legendary Creature — Dragon Avatar{4}{W}{U}{B}{R}{G}10/10
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.
Colour identity Five-color · Flying, Eminence · Commander page
In short
The Ur-Dragon has 7 listed printings; the most valuable is the Textured Foil printing from CMM at US$231.61 on TCGplayer's market price. Prices below are the cheapest in-stock listing in the United States.
Every The Ur-Dragon printing
Textured Foil
The Ur-Dragon
CMM · 1065
TCGplayer market
US$231.61
Foil Etched
The Ur-Dragon
CMM · 594
TCGplayer market
US$66.24
Secret Lair
The Ur-Dragon
SLD · 11
TCGplayer market
US$60.17
Borderless
The Ur-Dragon
CMM · 689
TCGplayer market
US$51.89
The Ur-Dragon
C17 · 48
TCGplayer market
US$37.01
The Ur-Dragon
CMM · 361
TCGplayer market
US$35.53
Future Sight
The Ur-Dragon
PF25 · 15
TCGplayer market
US$34.63