Threats in a post-apocalyptic world without mutants?

Question

So, today I asked a question about whether or not the mutants in my world were realistic Realistic mutated animals in a post-nuclear Earth? and apparently from the answers I got, they sadly weren’t, especially not the ones I wanted to have most (trihorns, giant scorpions, and skinless).

I mainly added them in to act as a threat for the surviving humans in my world to battle and fear. I want to know, if my world can’t have mutants, what can act as the looming threat to my post-apocalyptic survivors, because I desperately need some?

Answer 1

The most 'realistic' threat for your survivors to face is simply environmental factors - lack of access to safe water or enough food, and competition for resources against other more desperate and less morally upstanding people.

But from your suggestions, I'm thinking you want something more exciting. Depending on the history of your nuclear war, a good solution might be

The enemy that the nuclear weapons were used against

Regular people didn't get a lot of warning when the bombs fell, and they certainly didn't get a detailed understanding of why they fell. Your American survivors assume that Russia or China launched first and the US responded. Russian and Chinese survivors assume it was the Americans that went crazy. Nobody knows for sure, because any way of finding out was destroyed along with the rest of humanity.

Maybe:

It was one of those countries, and knowing they were about to start an apocalypse they put certain measures in place to protect their citizens and military - and now they're coming to claim the desolate landscape.

Or:

It was a threat nobody had considered - a supervillain or evil group that collected enough weapons, or at least influence over the people that own those weapons, to cause the disaster. Now the next step of their plan can begin.

Or maybe the threat was something else entirely:

A few days before zero-day, something appeared on deep-space monitoring scans. By the time the information reached the top levels of government, that something was already here, and spreading everywhere. Decisions were made, and countries fired on their own cities to defeat the threat. Your survivors never saw the something, but it/they survived, and it/they is still out there.

Or:

A horrifying disease that turns people into horrible monsters began spreading across the world. Selfish leaders decided that the best way to protect themselves was to retreat to their bunkers and destroy everything else. Your survivors were in an isolated location and didn't experience the spread, but the bombs didn't kill all of the monsters - and they're hungry. There's also locations scattered across the world filled with the rich and powerful and their staff/servants/slaves, who may yet play a part in the future of the world.

Or if you really want what you mentioned:

A series of portals to another dimension began opening across the earth, and monsters began pouring out - trihorns, giant scorpions, skinless to name a few. The governments of the world all reacted at almost the exact same time and launched their nuclear weapons against the threat, devastating the earth. While this was successful in closing the portals, the creatures remain.

Answer 2

The fact that it's post-apocalyptic is dangerous enough by itself

Firstly the reason for the world to collapse may still be present, or still have consequences:

• Nuclear mayhem? You've got nuclear fallout.

• Society collapse because it can't handle global warming with fewer ressources? Well, bad news for you, impact of global warming is still there.

• Asteroid impact? You now have a permanant harsh winter.

• Paperclip maximizer AI start a massive revolt against humans? the AI still want to kill you, even if society collapse.

But even if environment remain intact, just see how we strugle for millenia: everything is a reason to die.

Seriously, lot of people don't realize how current technology save our lives. You can die because it's too cold. You can die because it's too hot. You can die because of animals. You can die because of infection after what is considered a small injury today. You can die of illness. You can die because you don't have enough food, be it because winter, because hail, drought or freeze destroyed your plantation, or any other reason.

There is a reason for the life expectancy to go from 30 years to 70 years after industrial revolution. And you lost almost everything that keep it at 70 years. Good luck surviving this new world

Answer 3

People.

Look at Walking Dead. Yeh, zombies, but they are kind of like bad weather. They are not malicious. They are totally predictable. They are obstacles to be surmounted or evaded or worked around. The scary things in Walking Dead are other people.

In your post-Apocalyptic world survivors will have grouped together into whatever works to keep them alive. There will be regular people doing the best they can. There will be cults and warlord bands. There will be Mad Max type loners of varying sanities. Other people need the same things you need and they will try to take those things from you. Or they will try to convince you to help them, or beg you to. Other people do terrible things to outsiders to reinforce tribe solidarity. Other people acting sick and crazy are terrifying, because maybe you will get sick and act crazy too.

Monsters can keep it fresh, as they do in Walking Dead. Go ahead and have monsters. But energy in a story about humans comes from human interactions because those are the most meaningful to us.