Cheapest priced copy (The List): $0.35 at Card Kingdom, near mint, their price list as of .
Trollbred Guardian 
Creature — Troll Frog Warrior · 5/5 · Uncommon · Ravnica Allegiance · #148
{2}{G}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)
Each creature you control with a +1/+1 counter on it has trample.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
2 printings · $0.35 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| The List | RNA-148 | Uncommon | $0.35 | — |
| Ravnica Allegiance | 148 | Uncommon | $0.35 | $0.79 |
2 rulings from Wizards of the Coast
- 25 January 2019If a creature somehow loses all of its +1/+1 counters, it can adapt again and get more +1/+1 counters.
- 25 January 2019You can always activate an ability that will cause a creature to adapt. As that ability resolves, if the creature has a +1/+1 counter on it for any reason, you simply won’t put any +1/+1 counters on it.