// Threshold - {G}, {tap}, Sacrifice Centaur Garden: Target creature gets +3/+3 until end of turn. Activate this ability only if seven or more cards are in your graveyard.
Ability thresholdAbility = new ConditionalGainActivatedAbility(Zone.BATTLEFIELD,
new BoostTargetEffect(+3,+3, Duration.EndOfTurn),
new ManaCostsImpl("{G}"),
new CardsInControllerGraveCondition(7),
"<i>Threshold</i> - {G}, {T}, Sacrifice {this}: Target creature gets +3/+3 until end of turn. Activate this ability only if seven or more cards are in your graveyard.");
thresholdAbility.addCost(new TapSourceCost());
thresholdAbility.addCost(new SacrificeSourceCost());
thresholdAbility.addTarget(new TargetCreaturePermanent());
this.addAbility(thresholdAbility);