So in the new story I'm developing, some post-Earth settlers have colonized a new planet. A very small colony of world-leader billionaire types have brought a larger number of lower-class Earth citizens as slaves. (This isn't divided up by any demographic like race/gender/orientation or anything like that, purely on tech-determined fitness to work. The fascist class administered tests to find out who was most competent at the types of labor they needed, and hauled them off when they left Earth.) The planet has a dome over it to make the oxygen/pressure/etc like that of Earth, so people can live and breathe normally. The fascists live on a mountain plateau on the new planet, in luxurious huge mansions completely safe from the rest of the planet. The slaves live below the mountains, forced to do the labor based on areas/specific skills, but deprived of resources so they can't rise up (sort of how the 13 districts are in Hunger Games) Eventually, they start a revolution, which launches the main plot. In addition to the fascism and injustice of this whole system, what else would make the planet a really scary place for the people who live below the mountain? In terms of resident alien predator animals, geographic features about the planet (like Bolton Strid-style rivers, or frequent severe earthquakes, or volcanoes) or plot issues? In addition to the oppression and bad quality of life, what features about the planet itself would make the lower class's life on the planet scary, in a horror/action type of way? Also, whatever is formidable about the planet could ideally be used against the fascists somehow in the revolt. Thanks for any ideas!