“ 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.”
“ The PCs encounter a strange set of artistic drawings done on the ground as they pass through a city. It has been done in chalks and no one saw who did it. Wizards might recognize the writing within the colored square as an obscure and dead language with a message stating that a prominent wizard and a retired bard have discovered how to populate Arcadia with the spirits of the dead!
Is it a local hoax, or are the PCs crossing the path of a very deranged and possibly dangerous mage?”
“ A basin type hole in the middle of the plains. Once every so many years the rains come very hard and flood this place. Maybe that is where the tribes congregate for their tribal meetings.”