In this post-apocalyptic world, what drives one to investigate the horror? Why not simply avoid it, trying to survive amongst the ruins as best you can?The answer is the goal. Something makes
uncovering the truth more important than your life or your sanity.
In a Great War campaign, goals are particularly important. After an apocalypse, most people would run from danger, but the PCs must head towards it. If there are giant monsters emerging from the River Euphrates, the story requires that, somehow or other, people are there to observe them. If all the player characters retreat inland, as sensible people would, things become dull.
Antiquarianism:
Because of the apocalypse, unimaginably old artifacts have risen to the surface. You are captivated by them. Sometimes, you wonder whether you are living in the present or the past: certainly, when you look around, all you see is an ancient, decaying world. No matter. You must explore further and delve deeper into history.
The character is motivated by the search for ancient artifacts, the Ark of the Covenant being a major one.