The 'shimmer' effect is something that is found as a selectable option in several reverb pedals, but to have a whole pedal dedicated to it is more unusual.
Basically, this is a reverb pedal, based on the Wet, that can have variable amounts of shimmer added to the effect - the shimmer being created by an octave pitch transposer, delay and filter.
While the Mix knob is set up to go from 100 per cent dry to 100 per cent wet mix, and the Depth knob controls the length of the reverb tail (effectively the size of the simulated space), Shim adds in the shimmer: at its fully counter- clockwise starting position you get reverb only.
Bypass works as normal but a long press on the footswitch adds or removes shimmer from the mix with a pleasant fade-in/out. This pedal is aptly named: the sound is heavenly, a multi- dimensional illusion of massed high- pitched strings behind your tone.