Beware of towns afflicted with Time Cancer.
For every second you progress through time, an infected town goes back 48 hours. Old buildings slowly become new, then incomplete, and finally just a frame and foundation, giant old trees turn to saplings, birds hatch into eggs.
one must not linger in a chrono-cancerous village for too long, before you know it you'll be a fetus. Tme cancer in unstoppable, no cure or treatment is knwn, it eats through the past until the inhabitants of a village turn into primordial protein ooze
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.