Rey Dau

When a charged wing or tail of Rey Dau touches the ground, fulgurite forms on that part. Keep an eye on those growths. Once fulgurite has formed, the wing and tail produce wider swings and a stronger charge. Break those parts before the charge can build. After a big discharge, the head can be vulnerable, so that is the moment to press the attack. Seeing as the monster relies on thunder, bring armor with Thunder Resistance and weapons that deal Ice damage. Knowing when to use which element is key.