There is a submerged research facility in the southwest corner of the world map. Zell will be in your party, and he will tell you a story about it, and you might as well just let him tell it because if you say no, he'll still tell you. It is filled with fire creatures, so junction blizzaga to your elemental attack and firaga to your elemental defense. Stay still when the light rotates and mover when it is dimmed. Examine the front of the light source. To the first question, choose the first option, you will fight a Ruby Dragon. To the second question, choose the second option. You will fight another Ruby Dragon. To the third question, choose the secret, invisible third option to fight Bahamut. Use Aura, Triple magic and GFs to get rid of him quickly. You can draw Curaga and Full Life. He will join you. His "Rare Item" ability makes rare items easier to get from enemies that give them, so do this before you go on the quest to find the items for your ultimate weapons.