Cheapest priced copy (Duel Decks: Speed vs. Cunning): $0.35 at Card Kingdom, near mint, their price list as of .
Aquamorph Entity 
Creature — Shapeshifter · */* · Common · Planar Chaos · #33
As this creature enters or is turned face up, it becomes your choice of 5/1 or 1/5.
Morph {2}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
Legal inCommanderModernLegacyVintagePauper
Not legal inBrawlStandardPioneer
2 printings · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Speed vs. Cunning | 54 | Common | $0.35 | — |
| Planar Chaos | 33 | Common | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 1 February 2007If a creature enters as a copy of a face-up Aquamorph Entity, or a Vesuvan Shapeshifter turns face up as a copy of one, the controller of the creature entering gets to make the choice.
- 1 February 2007If a creature that's already on the battlefield becomes a copy of a face-up Aquamorph Entity, its power and toughness become the power and toughness that were chosen for the Entity.
- 1 February 2007The first ability is a replacement effect. The choice is made as Aquamorph Entity is turned face up (or enters); it turns face up (or enters) as a creature of that size. It doesn't become a 0/0 and then a creature of the chosen size.