Cinderella has 500,000 HP and is a straightforward magical nuke. She only has a 50% resistance to stun, so consider abusing that. Your best bet is to stack Light and Fire resist and debuff her MAT to tank her spells while you deal damage. Her unavoidable spells ignore your magical resistance, so don't bother. When she hits 15% HP, be prepared to dodge Daybreak. Unlike many other end-game bosses, she has no physical or magical resistance herself, so she's actually very fragile in comparison.
Actions:
- Holy Light: Light-element magical attack that debuffs MDF
- Jack-o-Lantern: Unavoidable Fire-element attack that cancels non-weapon-specific buffs/states
Below 50% HP, she gains one additional action per turn and no longer uses Jack-o-Lantern, but gains:
- Dancing Light: Unavoidable Light-element attack; also used as her counterattack
Below 15% HP, she no longer uses Holy Light, but gains:
- Inner Strength: Unbreakable charging state. Grants 5x MAT and 100% crit chance, plus an extra action per turn.
- Daybreak: Always used after Inner Strength. Will absolutely annihilate you if it hits, but you can dodge it.
She starts the battle with a constant counterattack state and switches between that and magic reflect every 10 turns (not actions per turn) taken by either her or you. Attacks and skills used with weapons that "never miss" (Storm Ruler and Miranda's Axe) will hit her through her counterattack state, as will Gun Break attacks.