The blackboard of the middle ages
A large steel shield in the form of a sea-shell attributed to Athena, the goddess of civilization, craft wisdom and war.
A Castle or better a fortified tower is floating over the country side and being attacked by goblins (or other monsters, depending on PC strength)
A world where most people know a few cantrips and even non-magical people can help to cast spells. Which is just as well because the big spells can only be cast with the help of large numbers of people.Most large spells tend to protect borders and stop earthquakes as they can be done legally, but there are those willing to cast bad large spells s well.A major part of law enforcement in this world is preventing evil magic.