This power includes the ability to permanently change ones appearance, slowly (over months) and with some effort of constant concentration You can only accurately substitute yourself for another person if you’ve had close contact and the opportunity to practice. Partial shifting of features, like moving your facial proportions around so that you are no longer recognisable, is easy. However, doing this analytically, for example, trying to turn your hair red by picturing the colour you want, doesn’t work. Instead, you should try imagining some other red-headed character, someone you know well, concentrate on their hair, and then imitate the person. Alternatively, characters may choose specific parts of their body to shift until it is done. It also allows faster changes which wear off if the user sleeps, falls unconscious, or otherwise stops maintaining them. This ability does allow a shapeshifter to mimic the appearance of others (with study) but only physically - there is no imitation of mind or psyche.