Cheapest priced copy (Battlebond): $0.35 at Card Kingdom, near mint, their price list as of .
Enduring Scalelord 
Creature — Dragon · 4/4 · Uncommon · Dragons of Tarkir · #222
Flying
Whenever one or more +1/+1 counters are put on another creature you control, you may put a +1/+1 counter on this creature.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
6 printings · $0.35 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Battlebond | 221 | Uncommon | $0.35 | $1.99 |
| Commander 2016 | 196 | Uncommon | $0.35 | — |
| Commander Anthology Volume II | 155 | Uncommon | $0.35 | — |
| Dragons of Tarkir | 222 | Uncommon | $0.39 | $1.49 |
| Midnight Hunt Commander | 149 | Uncommon | $0.35 | — |
| March of the Machine Commander | 325 | Uncommon | $0.35 | — |
3 rulings from Wizards of the Coast
- 25 February 2015A creature entering the battlefield with one or more +1/+1 counters on it will cause Enduring Scalelord's ability to trigger.
- 25 February 2015If +1/+1 counters are put on multiple creatures you control (other than Enduring Scalelord) at the same time, Enduring Scalelord's ability will trigger once for each of those creatures.
- 25 February 2015If you control two Enduring Scalelords, putting a +1/+1 counter on one of them will cause the ability of the other one to trigger. When this ability resolves, you'll put a +1/+1 counter on the other Scalelord. This will cause the ability of the first one to trigger. This loop will repeat until you choose not to put a +1/+1 counter on one of the Enduring Scalelords.