The armageddon spell is the fastest way, but remember to heal before you go looking for survivors, because you will also be wounded. It takes about six castings to destroy all the devils and twice this todestroy the titans and dragons. We are only talking about devils right now however. If you do not have access to enough armageddon spells then I have a simple answer. don't worry amount mage. Cast all your protective spells before entering the area (especially regeneration) and be sure to carry a lot of healing potions. Then just charge in, using only melee combat. Devils fall fast to strong, physical attacks. Knights and monks make quick work of most of them in my experience, but even weaker melee characters can clear a good number before they take serious damage. Still, keep fly going and always remain in the air, high enough so that the meteor showers do little damage, but low enough to attack. Even with four wizards it only took me about twenty minutes to clear the area (and this was before I was capable of facing dragons or titans).
