If you have to ask for tips from every boss you face, your problem may be you don't have enough levels. The Highbridge (where you are now) is the best place to gain AP for quite a while.

This boss has three stages. In the first, he uses elemental spells, which can be defended against using Element -Ward and -Proof armor. When you damage him enough, he'll start using Break to petrify your characters. Unleash your Aeons' ODs now to get this stage over with. In the third stage, he uses Flare. When this happens, you're almost there. BTW, remember to steal some Tetra Elemental from him.