The EarthQuaker Devices Afterneath is a genuinely creative and original effects pedal
Technically a reverb pedal, it achieves the effect by cascading what sounds like thousands of micro-delays that can be stretched, dragged and dampened to create various atmospheric textures.
Diffuse blurs the repeats that make up the reverb from sharp to soft and washy, while Reflect turns up the regeneration for an effect that lingers longer and will self-oscillate. Drag separates the delay lines ranging from 'a bunch of delays piled on top of each other' to a dense reverb.
The overall result is a pedal that delivers massive crystalline washes of sound.