Artifact Creature — Shapeshifter */7-*, 6 (6)
Uncommon
As Shapeshifter enters the battlefield, 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.
Illus. Adrian Smith

8/1/2008: The 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.
8/1/2008: The ability that lets you choose a new number is a triggered ability that triggers only once each upkeep.
Legal in Vintage (Type 1)
Legal in Legacy (Type 1.5)
Legal in Classic (MTGO)
Legal in Commander