Wishes are fun, but they’re tricky to adjudicate. You’ll use them more if you keep them simple: a wish can duplicate the effect of any spell or potion in the campaign. The heroes don’t have to have encountered the spell or potion. The lower the level, the bigger the area or duration—maybe even make it permanent.

Of course, popular wishes would be for money and magic items, and–at least in my campaigns–such things can’t be conjured by a magic.

• If a hero wishes for wealth, the people of a barony are charmed into believing the character is the rightful baron and start paying him or her rent… but the old baron and his cronies still think he deserves to be baron and so become enemies.
• If the hero wishes for a magic item, he or she gets a vision of where to find it… with trouble matching its power.