TIPS: HOW TO DEFEATE RUBY WEAPON
Ruby WEAPON appears once Ultimate WEAPON has been destroyed. You'll find it peaking out of the sand surronding the Gold Saucer. To initate combat fly into its head and it will surface.
Unless the WEAPON's claws are buried in the sand, its torso is invulerable. Attacking it such at a time will prompt Ruby WEAPON to use its quicksand attack that will instantly eliminate a member of your party. Typically Ruby WEAPON will use this attack twice, cutting your party down to one. This, of course, makes the battle a lot tougher. Once Ruby WEAPON burties its, attack the torso at full force- Quad Magic and Bahumat ZERO works pretty well, but Knites Of The Round Table summon will only prompt Ruby WEAPON to retatiate with Ultima. Be sure you equip your characters with the Final Attack--Revive combination or you won't stand a chance.