The Ur-Dragon is a mythic Legendary Creature — Dragon Avatar card from Commander Masters (CMM), collector number 689. Current market price: $51.80 (foil $52.97), TCGplayer market prices via Scryfall.
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.