Wife of Siglud and descendant of Heim through her father Prince Kurth and of Maira through Cigyun, and also the half sister of Alvis.

She was a villager living in a small village in the Spirit Forest in Verdane, the setting of Chapter 1. When Siglud met her in the forest, she was not allowed to associate or contact with men, but fell in love with him, and were wed in Agustria. She gives birth to Celice between chapters 2 and 3, and Celice inherits Minor Naga blood from her.

After Siglud captures Madino Castle during Chapter 3, Diadora tries to join him and the others in battle, but as soon as she was trying to reach him Manfroy captures and brainwashes her, and leaves her for Alvis to find in order to have them bear children who would serve as the vessels of Loptous.