Cheapest priced copy (Avatar: The Last Airbender Eternal): $1.79 at Card Kingdom, near mint, out of stock, their price list as of .
Scout's Warning 
Instant · Rare · Future Sight · #16
The next creature card you play this turn can be played as though it had flash.
Draw a card.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
2 printings · $1.79 to $59.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Future Sight | 16 | Rare | $5.99Out of stock | $59.99 |
| Avatar: The Last Airbender Eternal | 6 | Mythic | $1.79Out of stock | $2.49Out of stock |
4 rulings from Wizards of the Coast
- 15 April 2013You don't choose a creature card when Scout's Warning resolves. Rather, this sets up a rule that is true for you until the turn ends or until you cast a creature card, even if you cast that creature at a time you normally could.
- 15 April 2013If you cast multiple Scout's Warnings on the same turn, they'll all apply to the very next creature spell you cast.
- 15 April 2013You cannot use this effect to play Dryad Arbor during an opponent's turn.
- 15 April 2013After Scout's Warning resolves, you can suspend a creature card in your hand any time you can cast an instant. As soon as you actually cast a creature card, you lose this capability.