I more or less consider Warmech to be a secret boss in this game, He's harder than the Four Fiends and he gives 8x the Exp and Gold Tiamat (stongest of the four) gives upon death. From what I read online, you have a 1/64 chance to run into Warmech on the top floor of Tiamat's Floating Castle. Needless to say he went really easy on me in this fight. Everytime I've fought Warmech he started out with a high powered physical attack 150-450 damage (depending on your defense and if he lands a critical) or Nuclear which can do 200-400 damage to everyone. Some people say he can attack twice in one turn but he's never done that to me before but still, be cautious of that. Try to keep your hit points up as much as you can because he can wipe your party out really fast. Cast FAST on your primary melee characters if you can. Warmech doesn't have any weakness and he has around 1000hp.