Text (5th+errata): */*. ; ~this~'s power and toughness are each equal to the number of non-Wall creatures you control. [Oracle 2000/02/01]
The power/toughness adjusts itself as a continuous effect that is recalculated after each effect resolves or anything happens which might change it. [D'Angelo 1994/06/01]
Note - This card was creature type "Lord" until Oracle 2007/09/01 when it became "Human Barbarian".