Instructions
Raise your HP, or hit points, before battle. Level up and equip HP-raising items such as the Black Belt and Battle Boots. Behemoth unleashes powerful attacks and you will need high amounts of HP to withstand them.
Bring Quina to battle. Quina uses blue magic; the character's Roulette spell is an effective way to deal damage to Behemoth.
Equip Zidane with the Sargatanas blade. Use his Soul Blade skill to damage Behemoth.
Cast the Mini spell during the battle. Behemoth is weak against the Mini spell, although your chances of successfully casting the spell are random. However, when you successfully cast the spell, Behemoth will shrink and become more susceptible to damage. He will also cause less damage to your characters.