Sand, petrified woods, ruins of old settlements, no green except for the acidic pools that have formed from the spillage of the old war machines. This is the outside world, people only come here for one of two purposes, either to travel between massive self-sustaining cities or to gather resources.
But resource gathering is dangerous. The fauna of the outside, with a lack of sustainable food sources, has developed into a hunt or be hunted environment. The massive constructs of the ancients, powered by sunlight, roam the desolate desert dunes endlessly during daylight and have no other understood purpose than to end intelligent life. When the dim light of the moon sneaks past the dusty clouds the cursed dead of the ruins awaken to once again walk the forsaken lands they once inhabited, if you are unlucky enough to witness them, it will not take long for you to join them in their endless cycle.
With an unforgiving outside environment, only the most skilled and foolish leave the safety of the cities. The few that do lave have been dubbed Outwalkers and are seen as either heroes or suicidal idiots. What will you be seen as?