FOILCheapest priced copy (Mystery Booster 2): $44.99 at Card Kingdom, foil, near mint, their price list as of .
Tenacious Pup 
Creature — Wolf · 1/2 · Uncommon · Mystery Booster 2 · #262
When Tenacious Pup enters the battlefield, you gain 1 life. You get a one-time boon with "When you cast a creature spell, that creature enters the battlefield with an additional +1/+1 counter, trample counter, and vigilance counter on it."
Not legal inCommanderBrawlStandardPioneerModernLegacyVintagePauper
1 printing · $44.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Mystery Booster 2 | 262 | Uncommon | — | $44.99 |
One ruling from Wizards of the Coast
- 8 November 2024A one-time boon is a single-use triggered ability with no source. Once it triggers, it won’t trigger again.