They're the 2nd hardest nightmares to defeat. They can only be hurt from the back. They have a curse aura that causes your arts to backfire. It's good to hunt them in a team. Always keep your FreeAction up, they shoot a paralyzing chakram that will stop you on your track and they'll keep inflicting damage meanwhile. If you manage to defeat them, they'll reward you with 2,500 XP points.