Artifact, 4 (4) Serrated Arrows comes into play with three arrowhead counters on it. At the beginning of your upkeep, if there are no arrowhead counters on Serrated Arrows, sacrifice it. {T}, Remove an arrowhead counter from Serrated Arrows: Put a -1/-1 counter on target creature.1
Illus. David A. Cherry
The counter is removed as part of the cost of using the ability and is not returned if the ability is countered or if the target creature is not legal on resolution. [D'Angelo 1998/08/11]
The upkeep trigger only counts the number of counters at the start of upkeep. At that time it decides whether or not to put the ability on the stack. [D'Angelo 1999/08/01]