Fanaticism can be just as dangerous as fire. Spreading like fire, it could spark rebellion and could lead towards violence. As a way to curb devotion to the abstract, king Hareth of Garilroot asked his Mages to come up with a solution for those too invested in an ideal.
The secret for immortality has been discovered by an eccentric wizard/mad scientist. Its found you need to reapply once a month. As people stop dying, and the birth rate increases exponentially, people are forced into homelessness, because of the need for food reamins the same, and food is not being produced fast enough to feed the undying population. The PCs have to find the creator and kill him, and destroy production, to save the world from undying, unending torture from hungryness.