“ Believable magic, like ordinary physicis, operates according to some invariable laws that always result in some kind of cost or 'bounce back'. The grater the magic, the more it should cost the character physically, emotionally, and spiritually.”
“ What if potions and tonics had negative side effects? Potions of increased strength cause violent tempers, or damage joints. What if potions of dexterity caused tremors, or palsy?
What if they were addictive, and had withdrawal symptoms?
Could someone make a bad batch? No one use the brown strength potion!”
“ The devil's wind. Explains why people become crazy. They are caught up in this wind which steals their sanity which in turn feeds the wind. The wind is a leftover from when the air elementals banded together in a mass army at one point to attack the True Gods. The wind is leftover of their attack route and on the anniversary of the battle the wind sweeps through causing the madness.”