I think a druid could cause problems in a city that aren't too dark but still fun to solve.
Here are some ideas:
Four-Legged Thieves:
A band of thieves has been stealing valuables from right under the nose of an important merchant. When investigating, the group finds no human footprints, but instead animal tracks. A druid has Awakened a bunch of stray animals (a horse, a dog, a cat, some squirrels), and they have become a band of thieves. How to stop them from their spree? Help them spring their friend, an Awakened pig, who is going to be roasted at a big fancy party tonight!
River of Gold:
The characters come upon a mob of townsfolk bearing cups and bowls as a literal river of melted gold pours from a bank! This bank has been targeted by the druid who, invisibly, had cast Heat Metal on a gold delivery. The bank hires the characters to guard their next delivery of gold on its trek through the city, though the druid throws everything it can in their path: plant growth, swarms of animals, and some big conjured animals that can make a mess of the city.
Reading Roots:
The books in the central library have started reverting into trees! They are sprouting leaves and roots! Even more worrying, the words on the pages are disappearing! The roots lead down into an an old brick sewage system, and eventually to the lair of the druid. The characters find out that the city was built over some ancient standing stones. Through his magic roots the druid is absorbing all the knowledge of the city, and will use that knowledge to bring the city down! The characters could fight or offer to negotiate with city leaders.