Here's an idea: a mirror which spontaneously removes all the calcified material/tissue in anyone who faces it. This disappearing material instantly reappears near the mirror as a block which is subsequently shaped into a sculpture. All the while, a disembodied voice exclaims things based upon the individual, such as "marvelous!", "such wonderful hips!", and occasionally, things based on the individual's personality/past.
The mirror does not necessarily do this for all individuals, as those with too little calcified material are 'rejected'. The voice appears most attracted to those which it believes to be "big-boned".
Expressing ideas isn't my strong suit.
P.S. The completed sculptures are meant to 'represent' facets of the individual's personality, according to the voice. Also, mirror completely removes all calcified material, so the individual ends up dead.