Cheapest priced copy (Khans of Tarkir): $0.49 at Card Kingdom, near mint, their price list as of .
Crater's Claws 
Sorcery · Rare · Khans of Tarkir · #106
Crater's Claws deals X damage to any target.
Ferocious — Crater's Claws deals X plus 2 damage instead if you control a creature with power 4 or greater.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Khans of Tarkir | 106 | Rare | $0.49 | $0.49 |
| Khans of Tarkir Promos | 106s | Rare | — | $0.49 |
3 rulings from Wizards of the Coast
- 20 September 2014Ferocious abilities of instants and sorceries that don’t use the word “instead” will provide an additional effect if you control a creature with power 4 or greater as they resolve.
- 20 September 2014If you control a creature with power 4 or greater, Crater’s Claws with X equals 0 will deal 2 damage, with X equals 1 will deal 3 damage, and so on.
- 20 September 2014Some ferocious abilities that appear on instants and sorceries use the word “instead.” These spells have an upgraded effect if you control a creature with power 4 or greater as they resolve. For these, you only get the upgraded effect, not both effects.