Cheapest priced copy (Shadows over Innistrad Promos): $0.49 at Card Kingdom, foil, near mint, their price list as of .
Flameblade Angel 
Creature — Angel · 4/4 · Rare · Shadows over Innistrad · #157
Flying
Whenever a source an opponent controls deals damage to you or a permanent you control, you may have this creature deal 1 damage to that source's controller.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
3 printings · $0.49 to $2.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Shadows over Innistrad Promos | 157 | Rare | — | $0.49 |
| Shadows over Innistrad Promos | 157s | Rare | — | $2.99 |
| Shadows over Innistrad | 157 | Rare | $0.49 | $0.49 |
2 rulings from Wizards of the Coast
- 8 April 2016Note that the last ability is optional. Say two players each control a Flameblade Angel, and a source controlled by the first player deals damage to the second player or a permanent they control. The resulting triggered ability may deal damage to the first player, causing the ability of that player’s Flameblade Angel to trigger. That ability may deal damage to the second player, and so on. This cycle will repeat until the game ends or one player declines to use the ability, putting an end to the carnage.
- 8 April 2016If a source deals damage to you and/or one or more permanents you control at the same time, Flameblade Angel’s last ability will trigger that many times. For example, if a creature with trample deals damage to a blocking creature you control and you, Flameblade Angel’s ability will trigger two times.