I couldn't finish 'em. Looks like this's gonna get complicated.
It can use Holy, Holy Breath, Right Arm, Roar, Soul Despair and Thwack. The fight starts off easily as its attacks don't do significant damage. It uses Roar to stun all party members and Thwack, Right Arm, along with its normal attacks, to inflict damage. Brain Crush can inflict Confuse and Berserk to one target.
The fight gets harder when he casts Soul Despair. Soul Despair will not kill any member, but reduces their HP to below 10. After the first Soul Despair, it will use more powerful and dangerous attacks, such as Holy and Holy Breath, and it can cast Soul Despair again.
As soon as the battle start, Sophia or any White Mage should cast Shell, Protect, Haste and probably Regen. After receiving a significant amount of damage, Protector will begin casting Soul Despair. The next thing to do is casting Curaja or Healing Horn to recover the party. As its attacks are more powerful after this point, Sophia or a White Mage should be ready to cast Raise, Curaja. Healing Horn is also helpful in refill HP and cure Berserk and Confuse.