Cheapest priced copy (Rise of the Eldrazi): $4.99 at Card Kingdom, near mint, their price list as of .
Lightmine Field 
Enchantment · Rare · Rise of the Eldrazi · #32
Whenever one or more creatures attack, this enchantment deals damage to each of those creatures equal to the number of attacking creatures.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
1 printing · $4.99 to $32.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Rise of the Eldrazi | 32 | Rare | $4.99 | $32.99 |
4 rulings from Wizards of the Coast
- 15 June 2010Which creatures are dealt damage is based on which creatures were declared as attackers during the declare attackers step.
- 15 June 2010Lightmine Field’s ability triggers when any creatures attack, including your own.
- 15 June 2010For example: If a creature attacks but is removed from combat before Lightmine Field’s ability resolves (because it would be destroyed and regenerates, perhaps), that creature is dealt damage by Lightmine Field but isn’t counted when determining the amount of damage. On the other hand, if a creature is put onto the battlefield attacking (due to Preeminent Captain’s ability, perhaps), it isn’t dealt damage by Lightmine Field, but it is counted when determining the amount of damage.
- 15 June 2010How much damage each of those creatures is dealt is based how many creatures are attacking at the time the ability resolves.