Cheapest priced copy (Jumpstart): $0.35 at Card Kingdom, near mint, their price list as of .
Lightning Diadem 
Enchantment — Aura · Common · Jumpstart · #343
Enchant creature
When this Aura enters, it deals 2 damage to any target.
Enchanted creature gets +2/+2.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Jumpstart | 343 | Common | $0.35 | — |
| Journey into Nyx | 102 | Common | $0.35 | $0.49 |
One ruling from Wizards of the Coast
- 26 April 2014If Lightning Diadem's target is an illegal target when it tries to resolve, it won't resolve and won't enter the battlefield. Its triggered ability won't trigger.