The Great Divide

The Great Divide is a wound in the earth that spans miles across the Drylands, a massive crevasse deep enough that parts of it exist in perpetual shadow except at high noon. Old crumbling pathways lead down the steep sides into the darkness below, where hidden copses of edible plants and fresh water sources survive in the cool shadows of the canyon walls. For the survivalists of White Sands, these hidden resources are a lifeline, a secret supply that keeps the outpost alive in a desert that should have killed it years ago.
  Raiders have long since claimed the Great Divide as their nest. The canyon's depth and length provide endless hiding spots, defensible positions, and escape routes. The raider population has been growing for years, and the question is no longer whether they will overflow into the surrounding Drylands but when. The Asp Head Defenders guard the outskirts, but they are a thin line against a population that swells each season.
  Only the desperate or the skilled dare climb down into the shadows. The pathways are crumbling, the footing treacherous, and the raiders below have had years to learn every approach and ambush point. Those who make it to the bottom and back carry supplies that cannot be found anywhere else in the Drylands. Those who do not make it back join the shadows permanently.