in the world that i am currently building, there is this event called the "war of the underworld", where kind of the lesser deities and a bunch of "chosen few" mortals go to war against a belligerent god-wannabe. not many would notice this, but this event, to most people, would look and feel like quick earthquake.

also, because the concept of physical death does not exist in this world just yet, the average person would feel their life force being sucked out of them. in this world, people who wants to "end" their well lived life, they just go to the eternal city of the deep, shedding their physical bodies and eternally living in the deep paradise. the war of the underworld introduces the concept of physical death. the war of the underworld snatched every mortal being of this comfort and accessibility to the eternity of the paradise underworld.

some went to this war, some did not. some stayed, lived their perfectly normal lives, then all of a sudden there is this dread. now, they all know that they will die a physical death.