Six and Seven

Call it Hell, call it the Underworld, call it whatever you like, a lost soul known only as Six calls it "In" and he's stuck here. The souls of In spend their time feeding or fanning flames, watched over by strange creatures called Bellows, and staring through the constant snow of ash at seven distant chimneys visible at all times but eternally unreachable.

Then another soul called Seven gives Six some interesting news: You can get Out by climbing up through one of the chimneys, and Seven figured out how to get to them. Six and Seven set off across the ashy plains toward a chimney, and they quickly learn the rules. The only way to reach the chimney is to progress toward it metaphysically, by finding objects from their lives before In. But each object is accompanied by a painful death, which is followed by a memory from Six's life, and with each glimpse of what he left behind, Six begins to wonder if he truly wants Out at all.

Six and Seven is a horror novella that includes a short story sequel.