An ancient out of the way Imperial planet is forgotten about, warp travel to it sealed up by a nearby warpstorm. Intergalactic politics heat up, the other races have more pressing things to deal with. End up tucked into a footnote in history, and eventually the distant warp storm dissipates: the warp current making travel difficult to that sector fades away. Or does it?
in the mean time, the planet survives on its own, some keeping their faith in the emprah, some not. One faction in this world eventually finds a curious device buried in their planet: A Teleportarium, with strange, alien script buried in the sand along with the device. A manual, in lingo from the dark age of technology, or parhaps something else entirely?
It takes several years for the politial and military branches of the planet to figure out how the device works, but, curious about their heritage and intrigued by the prospect of meeting new and interesting people with strange technology to trade, a galaxy to explore and research, a decision is made:
For the first time in centuries, using the teleportarium, brave souls will set foot beyond the borders of their world, explore, investigate, and report back their findings. Armed only with their wits, common sense, and whatever scraps of advanced technology their world still possess, these teams will go forth to bravely go where everyone else has probably gone before, but with fresh eyes.
The problem is, this world may be sticking its noses into the politics of other races, and the races of the 40k universe do not like meddlers...
Especially when they've confused a webway gate for a teleportarium.