Whenever enchanted creature becomes tapped, Lust for War deals 3 damage to that creature's controller.
Enchanted creature attacks each combat if able.
6/15/2010 Lust for War’s triggered ability triggers when the enchanted creature becomes tapped for any reason, not just when it attacks.
6/15/2010 If, during its controller’s declare attackers step, the enchanted creature is tapped, is affected by a spell or ability that says it can’t attack, or is affected by “summoning sickness,” then that creature doesn’t attack. If there’s a cost associated with having that creature attack, its controller isn’t forced to pay that cost, so the creature doesn’t have to attack in that case either.