Cheapest priced copy (Fate Reforged): $0.35 at Card Kingdom, near mint, their price list as of .
Grave Strength 
Sorcery · Uncommon · Fate Reforged · #71
Choose target creature. Mill three cards, then put a +1/+1 counter on that creature for each creature card in your graveyard. (To mill three cards, put the top three cards of your library into your graveyard.)
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Fate Reforged | 71 | Uncommon | $0.35 | $0.49 |
| Foundations Jumpstart | 450 | Uncommon | $0.35 | — |
| Ultimate Masters | 101 | Uncommon | $0.35 | $0.49 |