Cheapest priced copy (Conspiracy: Take the Crown): $0.35 at Card Kingdom, near mint, their price list as of .
Kiln Fiend 
Creature — Elemental Beast · 1/2 · Common · Foundations Jumpstart · #139
Whenever you cast an instant or sorcery spell, this creature gets +3/+0 until end of turn.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
7 printings · $0.35 to $3.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Conspiracy: Take the Crown | 167 | Common | $0.35 | $1.99 |
| Duel Decks: Izzet vs. Golgari | 2 | Common | $0.35 | — |
| Iconic Masters | 137 | Common | $0.35 | $0.79 |
| Foundations Jumpstart | 139 | Common | $0.35 | — |
| Jumpstart | 338 | Common | $0.35 | — |
| The List | IMA-137 | Common | $0.35 | — |
| Rise of the Eldrazi | 153 | Common | $0.35 | $3.49 |
One ruling from Wizards of the Coast
- 15 June 2010Kiln Fiend's triggered ability resolves before the spell that causes it to trigger. The ability will resolve even if that spell is countered or otherwise leaves the stack.