I have Complex PTSD, and my 'others' have a similar structure - in my case a little girl who tries to be sweet and good and innocent so she can be looked after right, and a mean, hostile, protective persecutor that is defensive and aggressive and hates the whole world. Dialogue. Insight. Connection. Understanding. Nurtured by lots of intense therapy, and also personal written reflective work. I don't lose time/black out for long at all, in the scheme of things, which makes things easier to mediate, relatively speaking. One thing that helps me IMMENSELY is what is known as active imagination.