BL 13 Expert Mode
So now that I have a Leviathan, I still get OHKO'd on BL expert mode. I oftenly miss about 2 - 3 times in the sandstorm weather, then the sandstorm damage comes in and does MASSIVE damage to my Leviathan and usually kills it in 4-5 turns.

Here's my team as of right now:
Leviathan(Water Therapy II) - Bet mostly on DEF/MDEF
Water Bombs +1
Power of Darkness
Rain Prayer
Water Torrent
Bahamut(TFoN) - Bet on ATK/MATK
Power of Darkness
Cunning +4
Soak
Curse
Bahamut(Night Killer) - Bet on ATK/MATK
Cunning +1
Cunning
Foresight
Nightfall
Fenrir(Blizzard) - Bet mostly on DEF/MDEF
Aurora Borealis +1
Mind Bending +1
Chill
Blizzard
