Alvadr's Helmet is a steel cap helmet (tier 3) in terms of statistics. The only way to acquire the helmet is by letting Eydis Asulfsdottir join the party, since she has the helmet equipped when she joins the party. If she wears the helmet, it will provide a mental resistance bonus of 11% instead of 6%.
Eydis' husband left this spangenhelm for his eldest son when he passed. She wears it now in honour of his memory.