Radio enthusiast summoned to a world of sword fantasy and immediately starts building a radio while doing traditional fantasy shit with a video game style UI that everyone can see and a goddess that tells them they can level up. By building a crystal radio, the protagonist realizes they're hearing weird things on the radio all the time. Eventually they work out there is a signal whenever they see a skill box or XP level up event.
They eventually triangulate the signal to a massive desert and mount an expedition but they start feeling sick. They realize that if they make the party wear a metal helmet as a faraday cage they no longer feel sick. They get into the desert to find a huge structure.
When they enter the structure, it projects a hologram because it can't manipulate their minds directly anymore. The structure was an automated alien spaceship meant to transport ancient humans for study but crashed on this planet.
Finding the planet has weird magic energy but is otherwise dead, the crashed spaceship's supercomputer has been running an automated routine to preserve the life of its samples until it can be rescued. The human brain has as many synapses are there are stars in the sky and combined with a network of satellites, it can flick a few million of them a second to make and create the fantasy game-esque displays for people to "level up" with.
However, the planet is unrecoverable even with magic. The spaceship can do a lot, it can even teleport people from Earth every so often, to try to save these people. However, the ship also has a routine to prevent the people from discovering what it really is. The reason they were feeling sick is a result of these overlapping objectives.
While the spaceship is quite intelligent, it still is shackled by its routines. But the protagonist's party is the only one who's managed to interpret it properly, overcome the subroutine to keep the humans ignorant, and instead of giving up on finding the truth, they showed up.
Their planet is at the end of its geological cycle, the tectonic plates are no longer moving, the oceans are turning to salty mud, the magnetosphere is fading away and the spaceship can no longer sustain the satellites to sustain an artificial magnetosphere to stop the sun's radiation.
The alien computer presents 2 options:
1, it can teleport their party to the destination alien planet it was headed to, they're several thousand years late however, there's no guarantee anyone is still waiting for them. The energy use would greatly reduce the spaceship's ability to keep up the artificial magnetosphere. If they can't find help, the planet dies with no warning of what is coming;
2, the dungeons the spaceship is making full of monsters are meant to be radiation shelters but the native wildlife keeps taking up residence since it has to use this "magic energy" to build them. They can try to convince the various kingdoms an apocalypse is about to come. And to move as many people as they can support underground to survive. The spaceship can help but not much.
Not sure what to do from here, I had this idea because of a migraine.
