Dark Tulpa

My world's psychic powers have a draw back that pulls one towards selfish and dark actions. Essentially there is a hidden power every psychic has (regardless of the number or strength of their talents) which gains strength whenever the psychic fails to successfully use their talents. When opportunities to take selfish actions arise, this hidden power can trigger and they make the more selfish choice. When they are asleep the power may cause them to sleep walk and engage in aberrant behaviour. At its fullest this power can physically manifest an evil twin of the psychic, who then goes out into the world, and attempts to be the biggest asshole they can be, acting out all the darker urges within the psychic's mind.