An Evolved Human Alter Ego is the presence of multiple personalities within one mind. One with this ability may be docile and harmless while one ego is present, but powerful and vicious while another ego is present. And perhaps an ego may be invoked based on what type of persona the user thinks the current situation requires (this faculty is called Jungian Shift). It is also possible that each personality comes with a distinct ability or distinct traces (like scent, fingerprints, etc.) within each personality, this is an aspect of Shape Shifting, along with possible transformation based on which personality is active. Sometimes one personality (the normal or dominant personality) has no anomalistic abilities at all.
One with this ability has multiple minds/mind templates, and as such, superhumans who try to affect the mind of the user of this ability will have a hard time doing so; while one mind may be affected, another faculty of this ability allows the user to simply switch to the other unaffected mind at will, so the first consciousness can recover safely.