The PURPLL is a phase-locked loop (PLL) type pedal. It can be used as a fuzzed out harmonizer, drone synth and more. Check out the videos and the manual linked here for more details.
Blem units are new pedals with some sort of cosmetic defect. Such defects may include: small scratches on the surface/paint, defects in the silk screen/minor engraving issues, and/or outdated backplates. The defects are typically minor but you can see some sample defects in the gallery linked here.
Blem units have the same warranty as standard/mint units, however they cannot be returned for cosmetic reasons.