Well, we know that the skin-spies infiltrated Atyersus, so they'd know that Achamian was a member (given the fact there are < 200 mandati). I think it wasn't so much the skin-spy recognizing Seswatha in Achamian, so much as the skin-spy knowing enough to recognize that Achamian was Mandati, and that Mandati were the enemy because they were implanted with Seswatha's spirit in some way. view post