// Devour 2 (As this enters the battlefield, you may sacrifice any number of creatures. This creature enters the battlefield with twice that many +1/+1 counters on it.)
this.addAbility(new DevourAbility(DevourFactor.Devour2));
// When Tar Fiend enters the battlefield, target player discards a card for each creature it devoured.
Ability ability = new EntersBattlefieldTriggeredAbility(new DiscardTargetEffect(new DevouredCreaturesCount()));
ability.addTarget(new TargetPlayer());
this.addAbility(ability);
}