Cheapest priced copy (Duel Decks: Divine vs. Demonic): $0.35 at Card Kingdom, near mint, their price list as of .
Serra's Boon 
Enchantment — Aura · Uncommon · Planar Chaos · #17
Enchant creature
Enchanted creature gets +1/+2 as long as it's white. Otherwise, it gets -2/-1.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Divine vs. Demonic | 18 | Uncommon | $0.35 | — |
| Duel Decks Anthology: Divine vs. Demonic | 18 | Uncommon | $0.35 | — |
| Planar Chaos | 17 | Uncommon | $0.35 | $0.49 |