Shadow Madarame is a unique boss fight involving four paintings: the 'Righteous,' 'Vengeful,' 'Gluttonous,' and 'Callous' paintings. Each painting has specific weaknesses: Righteous (Ice), Vengeful (Fire), Gluttonous (Wind), Callous (Electric). You must destroy all four paintings simultaneously. Use Joker to hit multiple weaknesses with multi-target spells, and have your party members focus on their respective elemental weaknesses. After destroying them, Madarame will reveal his true form. He has no elemental weaknesses but is susceptible to physical attacks. He will occasionally recreate the paintings, so be prepared to repeat the process. Keep your HP and SP high, as this can be a long fight. Yusuke's Ice attacks are invaluable here.
