Nanba excels as a magic user and debuffer. His default 'Homeless Guy' job offers powerful fire magic and status ailments. Consider switching him to 'Chef' for additional elemental damage and healing, or 'Host' for charm and debuffs. Focus on increasing his Magic and Agility stats. Nanba's ability to inflict status effects like Burn and Cold is invaluable against tough enemies, making him a crucial support and offensive caster.
