well, i beat them first time, but when i go to fight them the second time, i dont have any spells or protection left on my party and they just slaughter me...what should i do? or at least what are the best spells to use in the first battle against them...

Yes, you do need to conserve your spells. When i fight the twins in the first battle, my wizard and sorcerer used only crossbow and bolts. Besides, you have a few monks to help you.

finally beat em, i found out that its much easier to hit Isair than Madae, so i juts concentrated all my attacks on him...