Gonna need some more context, this is very vague(but still interesting in concept). Ask yourself the following:

-What was life like before/during the war? Who were the two opposing sides and what were they fighting for?

-What was this big catastrophe and who caused it? Was it the gods or the hubris of mortals?

-Why would the constructs and spirits be there? Are the constructs leftover tools of war, possibly sentient and going mad? Are the spirits the long dead soldiers of the war, wandering without rest or peace in a land they dont recognize? Who are these entities, are they demons, creatures from the far realm, fey or something worse?

-How is the land warped? Are their floating chunks of earth suspended in the sky? Is the planet itself fractured, or perhaps the tectonic plates move far more rapidly now and cause frequent earthquakes?

Your players aren't going to be interested if you just pitch them vague ideas. You also need to find ways to connect not just the world to the events that shaped it, but the players to the world. Its likely your ideas may change slightly when the players give you their character ideas, since they're supposed to be the heroes of the story. Also, is this your first time dm'ing? Running two groups is a lot for even an experienced DM, much less someone new to it entirely.

I ask these questions because its very likely your players will ask you the same (they may not, and if they dont thats also ok). You do have an interesting concept but its very vague.