“ What if cancer is not an ailment if one has a will powerful enough, and knows what do do. What if one using the right techniques could control it and use it to become immortal, or to grow into something else?”
“ What happens when, while in the middle of an important fight/Event, the mage that enchanted all your gear suddenly dies? Unless the enchantments outlive their source, you might not either.”
“ If you want to add a 'supernatural' touch to your campaign, define the rules of magic and the universe. Make your players comfortable with those rules. Then your new supernatural creatures must then break those rules.”