I dont know if this has been brought up but i think that the dark soldier was once a friend of ven, terra, and aqua but was then possesed but master xenahort who said he would grant him power. then i predict right after the secret kh2fm secret ending an event that happened in kh1 when riku wouldnt let ansem sod (seeker of darkness) destroy sora or kairi and broke free from him the same thing happned to dark soldierand something terrible happned to him. thts all flame if u want