// {U}, {tap}: Put a 0/1 blue Homunculus artifact creature token onto the battlefield.
Ability ability = new SimpleActivatedAbility(Zone.BATTLEFIELD, new CreateTokenEffect(new HomunculusToken()), new ManaCostsImpl("{U}"));
ability.addCost(new TapSourceCost());
this.addAbility(ability);
// At the beginning of your upkeep, sacrifice a Homunculus.
this.addAbility(new BeginningOfUpkeepTriggeredAbility(new SacrificeEffect(filter, 1, ""), TargetController.ANY, false));
}