Unstable Servo

Vanishing 3 (This creature enters the battlefield with
three time counters on it. At the beginning of your
upkeep, remove a time counter from it. When the last
is removed, sacrifice it.)

Unstable Servo's power and toughness are equal to
the number of time counters on it.

{3}: Add or remove a time counter from Unstable
Servo. Any player may play this ability during their
upkeep and only once per turn.