effect = new ConditionalOneShotEffect(new SacrificeSourceEffect(), new SourceHasCounterCondition(CounterType.ARROWHEAD, 0, 0),
"if there are no arrowhead counters on {this}, sacrifice it");
this.addAbility(new BeginningOfUpkeepTriggeredAbility(Zone.BATTLEFIELD, effect, TargetController.YOU, false, false));
// {tap}, Remove an arrowhead counter from Serrated Arrows: Put a -1/-1 counter on target creature.
Ability ability = new SimpleActivatedAbility(Zone.BATTLEFIELD,
new AddCountersTargetEffect(CounterType.M1M1.createInstance()),
new TapSourceCost());
ability.addCost(new RemoveCountersSourceCost(CounterType.ARROWHEAD.createInstance()));
ability.addTarget(new TargetCreaturePermanent());
this.addAbility(ability);
}