@pixel_player58486295 I haven't seen a task like this before, so maybe that is why it is confusing so many people. Merlin says there is one bell in each location. You'll find one bell in Shmek's Swamp, and you'll need to leave this map/location uncompleted while you go find the other seven bells, one in each of the other seven required maps/locations.
To open the next required map/location, you will need to visit the three optional "challenge" maps.
It confused me, too, for a bit. And I hated leaving a map incomplete. But it all worked out in the end! I hope this helps you.