Mulliganing hard (putting a lot of cards back to draw again) to have a play for turn 1 will make a big difference
If The Ur-Dragon itself hits the battlefield, the game is likely over
The biggest factors are the card itself, the grade, the grading company, collector demand, and recent sales of similar cards
Number 23 Language English Legal Formats Commander, Legacy, Pauper, Vintage Not Legal Formats Alchemy, Brawl, Competitive Brawl, Historic, Pioneer, Standard, Timeless Rulings (12/8/2022) You choose the target for Dread Return before paying any of its costs, so it's not possible to cast it using flashback and bring back one of the creatures you sacrifice
Most valuable cards in Phantasmal Flames View the full price guide Discover
Impetus Auras The impetus auras provide a wonderful boost to your creatures or incite chaos in a multiplayer game