Cheapest priced copy (Mystery Booster 2): $2.79 at Card Kingdom, near mint, their price list as of .
Scalelord Reckoner 
Creature — Dragon · 4/4 · Rare · Mystery Booster 2 · #151
Flying
Whenever a Dragon you control becomes the target of a spell or ability an opponent controls, destroy target nonland permanent that player controls.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
2 printings · $2.79 to $17.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2017 | 6 | Rare | $5.99 | — |
| Mystery Booster 2 | 151 | Rare | $2.79 | $17.99 |
2 rulings from Wizards of the Coast
- 25 August 2017If the only nonland permanents on the battlefield are Scalelord Reckoners and Dragons controlled by players who control Scalelord Reckoners, any spell or ability that targets one of those Dragons will cause an infinite loop of triggered abilities and the game will immediately end in a draw.
- 25 August 2017Scalelord Reckoner's triggered ability resolves before the spell or ability that caused it to trigger. The ability will resolve even if that spell or ability is countered.