Cheapest priced copy (Ravnica Allegiance): $0.35 at Card Kingdom, near mint, their price list as of .
Aeromunculus 
Creature — Homunculus Mutant · 2/3 · Common · Ravnica Allegiance · #152
Flying
{2}{G}{U}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.)
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ravnica Allegiance | 152 | Common | $0.35 | $0.49 |
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.