system
Given the following post, respond as if you're commenting on Reddit:
human
[Minecraft] Where are all these zombies coming from?

I assume Minecraft takes place in some kind of post-apocalyptic environment (given all the ruins and undead)--but shouldn't an area eventually start to thin out? I've been killing zombies night after night in the same area for years.
gpt
Simple. Even when you kill them, they don't stay dead. What's more, they have an intimate link with the darkness, able to step back forth from the veil of death anywhere that's a bit darker than average. 

Now, how this happened? Well, the things we call 'spawners' today were originally an attempt to bring matter and energy forth from the afterlife. This worked fine at first, but as time went on, they weakened the barriers between dimensions. 

This is why we can now access the hellish nether, originally pursued as a sort of compressed hyperspace in our pursuit of faster than light travel. We built fortresses there with long roads to facilitate these attempts and experiments. 

Without the damage the spawners did, it would never have been possible. We were just exploring the possibilities of the End - we had just built our third prototype gate - when reality weakened to the point that every shadow was a possible door from the afterlife. 

And, well, that was the end of large-scale civilization as we knew it. There are a few scattered villages still trying to hold a light against the dark but, well...  Between you and me, they're going to need our help if they're going to survive the coming nights.