// Delve
this.addAbility(new DelveAbility());
// Flying
this.addAbility(FlyingAbility.getInstance());
// {X}, {T}, Exile X cards from your graveyard: Target creature gets -X/-X until end of turn.
DynamicValue xValue = new SignInversionDynamicValue(new ManacostVariableValue());
Effect effect = new BoostTargetEffect(xValue,xValue,Duration.EndOfTurn);
effect.setText("Target creature gets -X/-X until end of turn");
Ability ability = new SimpleActivatedAbility(Zone.BATTLEFIELD, effect, new ManaCostsImpl("{X}"));
ability.addCost(new TapSourceCost());
ability.addTarget(new TargetCreaturePermanent());