If used on a monster, you will cast one of ~5 skills. One of them, Class Change, will transform the mob into an MvP, one, Grim Reaper, will kill it, one, Gold Digger, will gain you some zeny, one, Beastly Hypnosis, will try to tame it, one, Monocell, will transfor it into a poring and if there's another one, I forgot it.