Cheapest priced copy (Commander 2015): $0.49 at Card Kingdom, near mint, their price list as of .
Firemind's Foresight 
Instant · Rare · Return to Ravnica · #162
Search your library for an instant card with mana value 3, reveal it, and put it into your hand. Then repeat this process for instant cards with mana values 2 and 1. Then shuffle.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.49 to $2.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2015 | 218 | Rare | $0.49 | — |
| Duel Decks: Mind vs. Might | 21 | Rare | $0.49 | — |
| Return to Ravnica | 162 | Rare | $0.49 | $2.49 |
2 rulings from Wizards of the Coast
- 1 October 2012You don't have to find any instant cards in your library, even if they are there.
- 1 October 2012If a card in your library has {X} in its mana cost, X is 0. For example, a card with mana cost {X}{R} has a mana value of 1, and so on.