Cheapest priced copy (Modern Horizons 2): $0.35 at Card Kingdom, near mint, their price list as of .
Aeromoeba 
Creature — Elemental Beast · 2/4 · Common · Modern Horizons 2 · #389
Flying
Discard a card: Switch this creature's power and toughness until end of turn.
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Modern Horizons 2 | 37 | Common | $0.35 | $0.49 |
| Modern Horizons 2 | 389 | Common | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 18 June 2021Because damage remains marked on a creature until the cleanup step or an effect removes that damage, nonlethal damage dealt to a creature may become lethal if you switch its power and toughness during that turn.
- 18 June 2021Effects that switch a creature's power and toughness apply after all other effects, regardless of when those effects began to apply. For instance, if you switch Aeromoeba's power and toughness and then give it +2/+0 later in the turn, it's a 4/4 creature, not a 6/2 creature.
- 18 June 2021Switching a creature's power and toughness twice (or any even number of times) effectively returns the creature to the power and toughness it had before any switches.