Cheapest priced copy (Fourth Edition): $0.35 at Card Kingdom, near mint, their price list as of .
Shapeshifter 
Artifact Creature — Shapeshifter · */7-* · Uncommon · Renaissance · #157
As this creature enters, choose a number between 0 and 7.
At the beginning of your upkeep, you may choose a number between 0 and 7.
Shapeshifter's power is equal to the last chosen number and its toughness is equal to 7 minus that number.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
36 printings · $0.35 to $10.99 at Card Kingdom
2 rulings from Wizards of the Coast
- 1 August 2008The ability that sets its power and toughness is a characteristic-defining ability. This means it applies before any other effects that modify power and/or toughness.
- 1 August 2008The ability that lets you choose a new number is a triggered ability that triggers only once each upkeep.