Instructions
Configure your party to include Glenn if you have obtained him before this point. With Glenn in the party, the spell X-Strike can be used with Serge. Only Serge and Glenn can use this attack and, when used, it deals upward of 300 damage to Fargo.
Use supporting spells such as TurnRed or Strengthen. TurnRed makes your character's attacks deal red element damage. Fargo, being a blue element character, is weak against red element attacks. Strengthen allows your characters to do additional damage with their basic attack.
Use red element attack spells such as Fireball or Fire Pillar. Both of these spells deal extra damage against Fargo due to his weakness.
Attack Fargo with basic attacks. With the supporting spells cast earlier, your characters deal additional damage with each attack.
Use spells such as HealAll after Fargo attacks to keep your party at full health. If Fargo casts Strengthen on himself, use spells such as Weaken to remove the strength gain he receives.
Attack Fargo until you have dealt 660 points of damage to him, at which point he is defeated.