Cheapest priced copy (Tarkir: Dragonstorm Promos): $0.49 at Card Kingdom, near mint, their price list as of .
Roar of Endless Song 
Enchantment — Saga · Rare · Tarkir: Dragonstorm · #390
(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Create a 5/5 green Elephant creature token.
III — Double the power and toughness of each creature you control until end of turn.
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
4 printings · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Tarkir: Dragonstorm Promos | 220p | Rare | $0.49 | $0.49 |
| Tarkir: Dragonstorm Promos | 220s | Rare | — | $0.49 |
| Tarkir: Dragonstorm | 220 | Rare | $0.49 | $0.49 |
| Tarkir: Dragonstorm | 390 | Rare | $0.49 | $0.49 |
One ruling from Wizards of the Coast
- 4 April 2025If an effect instructs you to “double” a creature’s power, that creature gets +X/+0, where X is its power as that effect begins to apply. Similarly, a creature whose toughness is doubled gets +0/+X, where X is its toughness as the effect begins to apply.