Cheapest priced copy (Foundations Commander): $1.49 at Card Kingdom, near mint, their price list as of .
Hellkite Charger 
Creature — Dragon · 5/5 · Rare · Zendikar · #131
Flying, haste
Whenever this creature attacks, you may pay {5}{R}{R}. If you do, untap all attacking creatures and after this phase, there is an additional combat phase.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
8 printings · $1.49 to $6.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Archenemy | 41 | Rare | $6.49 | — |
| Commander 2017 | 138 | Rare | $3.49 | — |
| Commander Masters | 232 | Rare | $2.99 | $5.99 |
| Commander Masters | 540 | Rare | — | — |
| Foundations Commander | 160 | Rare | $1.49 | — |
| Modern Masters 2015 | 118 | Rare | $3.99 | $4.49 |
| Salvat 2011 | 109 | Rare | — | — |
| Zendikar | 131 | Rare | $3.99 | $5.99 |
4 rulings from Wizards of the Coast
- 1 October 2009You decide whether to pay {5}{R}{R} as Hellkite Charger’s ability resolves.
- 1 October 2009Hellkite Charger’s ability may trigger multiple times in the same turn, since its own ability gives it multiple chances to attack. Each time it resolves, you may create an additional combat phase.
- 1 October 2009If you pay {5}{R}{R}, the new combat phase immediately follows the current combat phase. There is no main phase in between.
- 1 October 2009If two Hellkite Chargers attack at the same time, both of their abilities trigger. If you pay {5}{R}{R} for each, two new combat phases will be created. However, all attacking creatures untap as those abilities resolve, not as the combat phases start. Any creature that attacks in the second combat phase will remain tapped during the third combat phase.