MindRot

The city of the Kingdom of the Elements is surrounded by a city wall, for many reasons of course, but the main being to protect people from Gonneffs. Gonneffs are short creatures with stubby arms and legs, large mouths, and black eyes. Hairless, and carnivorous, it is long forgotten that this was once a peaceful people. Gonneffs are now known to have an uncontrollable need for blood. They live to kill anything that moves which is not a Gonneff. All the Gonneffs have been collected and captured over the last couple hundred years and brought under the city of the Elements to live. They are captives but don't mind as not much happens in their heads anymore.
When someone is banished from the city of the elements, the Gonneffs are released to chase them away from the city, and if they don't run fast enough, they eat them.
After about twenty minutes pass, they ring bells and the Gonneffs cannot resist crawling back under the city away from the sound of the bells.
Recently a scientist who has been studying their behavior for many years came up with the theory Gonneffs are peaceful creatures who are sick and even more recently he proved it when he cured one. Problem is, he is unsure what he did to cure the Gonneff exactly. He and the Gonneff are now campaigning around the kingdom of the elements to bring awareness and try to raise money to cure all the Gonneffs of MindRot.
Most people see them kind of like a traveling circus. It is difficult to persuade people this is not a parlor trick, a costume or just a trained Gonneff, but that the Gonneffs that they see running around hitting themselves on walls and getting lost because a bucket is on their heads, are simply sick with MindRot and need to be treated.