Think of Frodo and Galdriel's vial fighting shelob, decendant of ungoliant? Galdriel was a noldor who survive the bloody battle of rebelion. She wasn't no pocket nurse, she was an armed warrior. She was a powerful elf like all her kin. When ungoliant spits 'her spiritual poison' on the ground, being the only place she could put use to it, galadriels ring would protect her. Like i said, think about Frodo's fight then, magnify it by 1000. About turin, his sword was destroyed but if he had it, i bet it would be better then a westernese blade, and would still effect ol witchie, i bet sting wold have worked, or Gandalf's sword too. But if not, Turin would figure it out then he'll find his westernese blade and finish the job. Think about Beren fighting Melkor, He got away, turin would get away from the witch king if need be, only to return and smack him around. 🙂