Cheapest priced copy (Urza's Saga): $0.35 at Card Kingdom, near mint, their price list as of .
Rune of Protection: Green 
Enchantment · Common · Urza's Saga · #38
{W}: The next time a green source of your choice would deal damage to you this turn, prevent that damage.
Cycling {2} ({2}, Discard this card: Draw a card.)
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
1 printing · $0.35 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Urza's Saga | 38 | Common | $0.35 | — |
2 rulings from Wizards of the Coast
- 4 October 2004Can be used even when there is no damage to prevent. It prevents the next damage (if any) from the source this turn.
- 4 October 2004A source of damage is a permanent, a spell on the stack (including one that creates a permanent), or any object referred to by an object on the stack. A source doesn't need to be capable of dealing damage to be a legal choice.