I Want to Be a Receptionist in This Magical World Vol 8 manga

Nunnally and Rockmann go head-to-head in their Walhelnus duel, as she proves to everyone she has the power to take on a founder-level mage! But before a victor can be crowned—calamity erupts. Stadal, the ancient evil spoken of by demons, has broken through the barrier. Springing to action, the knights move to defend their nation and Nunnally from the invader. But can the combined mages of this kingdom truly hold their own against evil itself...?