We know from Rav Nahman that there are Torah scholars that are demons [LeM I:12.]. But how can they trick others? People are so easy to swindle because of the victim's own moral defects.  When good judgment and moral sense are subjected and by lust or greed or sloth or vanity or anger, the one swindled participates willingly in his own undoing.  In the end he swindles himself. 

There is a transcendent aspect of human life. There are however different sources of transcendence. Not all are good. So it makes sense that Rav Nahman would warn about this. Clearly also the Gra and Rav Shach also warned about this, but for some reason their warnings seems to go ignored.