Basically shadow is merged with ego but shadow is not under control of ego. Means shadow become part of conciseness, and You have now dual personality, like light and shadow, in opposite way. Two personalities in one, monster and prisoner. Dr Jekyll and Mr Hyde.
Shadow is huge and posses huge energy. And so long time shadow is repressed part of Self. So, it is logical that person become very egocentric, selfish. And all repressed - shadow now have to be realized and maintenance balance. That is the reason why shadow personality now is stronger and lead MLCer. He still wear mask - old personality. Person become treacherous and delusional. So, one can be possessed by shadow and gain more clarity when ego take lead. They are in neurotic state even in psychotic state. They use regression of ego as defense mechanism, use maladaptive coping mechanism and use immature defensive mechanisms.
Using so regressive immature defense mechanisms they doing extreme projections, including anima/animus. There come adultery... dreams, fantasies released.