From the Zochar Chai, Vayechi 377b
The sin of emitting semen in vain is encompassing and it damages the mazal of the person at the level of DAAT. Because the one who sins in this fashion, the image of G-d immediately runs away from him and he becomes a beast, damaging with anger, pride and all evil traits, a destroyer indeed, like one of the demons and even less than them, and his Torah and his prayers are broken by the Kelipot…and as long as he doesn't do Teshuva, he is like one who has no portion in the G-d of Israel and it is forbidden to talk to him.