Stratatonic, the Allegory of the Cave monster
Stratatonic (Strata + Platonic ~ Catatonic) is a Rock/Ghost Legendary member of the Lightbearer quartet, which are each based on thought experiments. This particular member is based on Plato's Allegory of the Cave: the impish shadow is an illusion that is easy to mistake for the actual creature, the rock slate it is cast onto. Stratatonic is actually quite gentle and meek, but the spark it carries projects its rascally inner desires into plain view.
Its unique ability Projection causes the user's self stat-lowering moves to afflict the target instead, or everyone else on the field in case of a self-targeting status move (although it isn't usually getting to use non-Ghost Curse or Shell Smash). It can also get Unnerve, courtesy of the shadow critter.