Afterneath sounds very much like what it sounds like: a wizard emerging from an ethereal cave and ready for ambient battle. You are the wizard - or sorceress, if you prefer - and the cave is the signpost to your vast, expansive, magical instrument. You enter, roll a D20 to continue! 
Once inside, you are struck by a glint of light from an unknown source and notice a strange glow on the cave walls. You approach the cave walls timidly. As you gently rest your hand on the cave wall, you feel the rock move - the cave is alive! Alarmed, you emit a loud, muffled cry that echoes throughout the subterranean landscape. Listening more closely, it seems that the reverberations of your voice are actually a swarm of short digital delays that can be used to create wild, cavernous reverberations, or sparse, short, rhythmic delays with strange characteristics.