In The Crystals, Titan deals heavy physical damage. After a few rounds Titan will use Gaia's Wrath. If the party has been to Mysidia and rescued Porom, she arrives to cast Float on them and save them, but if she has not been saved the fight ends with the party falling into a cave and they must fight their way out back to Agart. When the fight restarts, everyone has Float status to avoid Titan's earth attacks, but Float will wear off a party member if they are killed. Titan can use Crush now, instantly killing a party member.
When Titan is damaged enough he will come to his senses and the fight will end.
Lunar Curtains to grant Protect status to the party are helpful, and Edge can use Mirage to give himself Blink status. Luca and Edge should attack while Rydia and the Man in Black cast magic. Rydia should summon whatever Eidolons the player has rescued as they do more damage than spells. If the player found a Recovery Rod in the Lodestone Cavern, Rydia can use it as an item to heal the party as there is no White Mage in the group, otherwise she should be the party member to heal the others with Potions, as she likely has the party's lowest damage output. The InfernoBand does high damage if the player has acquired it yet.