Arbaroc (boss)

 Have about 4000 gil when you get to the room before Arborok, and the ransom ability on your merchants (gotten by enhancing the Merchant crown twice), along with the strongest defences you can afford, including resistances to light, wind, and earth wherever possible. Merchants should have books of Cure and Raise if there are non-merchants in the party. Hit Arborok with non-elemental damage, boosting when he's in the air and you should be able to outlast him before you drop below half your money.