Cheapest priced copy (Archenemy): $0.49 at Card Kingdom, near mint, their price list as of .
Flameblast Dragon 
Creature — Dragon · 5/5 · Rare · Magic 2012 · #133
Flying
Whenever this creature attacks, you may pay {X}{R}. If you do, it deals X damage to any target.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
7 printings · $0.49 to $0.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Shards of Alara | 100 | Rare | $0.79 | $0.99 |
| Archenemy | 38 | Rare | $0.49 | — |
| Commander 2018 | 123 | Rare | $0.49 | — |
| Game Night: Free-for-All | 77 | Rare | $0.49 | — |
| Magic 2012 | 133 | Rare | $0.59 | $0.49 |
| Salvat 2011 | 102 | Rare | — | — |
| Starter Commander Decks | 142 | Rare | $0.49 | — |
One ruling from Wizards of the Coast
- 1 October 2008You choose the target when the ability triggers. When the ability resolves, you choose a value for X and decide whether to pay {X}{R}. If you do decide to pay {X}{R}, it's too late for any player to respond since the ability is already in the midst of resolving.