Yeh, it took me a while to beat this guy. Actually, i had to re-play before i could beat him. My party contained Zidane (obviously), Quina, Steiner and Garnet/Eiko. The key is to equip each character with armour that absorbs shadow. There are two Pumice pieces available b4 fight him (one available from fighting ark at Oielvert, and the other from a chocobo treasure), so thats two of your characters sorted. There's an armour that Zidane and Amarant can equip that absorbs shadow (Dark Vest or sumthin like that), and i didnt find anything for Steiner (although im sure there's some out there) so I gave him armour that halves Shadow damage. I had Quina in my party from the start everytime s/he was available, and constantly took her to Qu's Marsh. I got so many frogs, that when I got to Ozma frog drop (10mp) did 9999 damage! Zidanes Thievery does damage based on how many treasures you have uncovered (I don't know exactly how this is measured), anyway mine did about 3000-4000 damage but i'm sure it could do more. Steiner's Climhazard is helpful for a mean 4000 ish damage, and i had Garnet/Eiko healing people after each of his attacks. Well, I hope that gets you started on your way to beating him. Geez, do ya think I shud of just put a link to a guide or sumthin?