In the world I am building (based heavily on the Star Wars universe setting, but more historical), humanity first abandoned Earth to travel to another planet within their solar system, which they christened "Nu Terra".
But an unknown reason lead the humans to leave Nu Terra within a month, using a unique crystal found there to travel through hyperspace (in a rudimentary way) to another galaxy (via another source of the crystal), from which they moved to Coruscant.
My main issue is that humanity is extremely hardy and would be able to adapt to/kill most dangerous creatures.
Another issue is that the main characters will be travelling there towards the end of the storyline, so the planet itself has to be reasonably intact and still showing obvious signs of population.
So my question is this: Why would humanity be so hasty to get so far away from Nu Terra using such an untested method? What could possibly await anyone foolish enough to go there?
- Nu Terra should appear normal (and abandoned) at first glance to anyone who travels there
- The danger should not be immediately obvious, but it should not take a character dying for them to know about it.
- The danger should still be present 50,000 years after the abandonment of the planet, when the characters return.