The Barbarian is a sharp turn after the Advocate: a path that began with procedures and eloquence, at the eighth step takes up brute force.
As it progresses, the bearer's body receives improvements that simply break the "rules" of an ordinary human organism: strength and constitution go beyond what is allotted to a human. Along with the body, the head also grows stronger — the Barbarian gains high resistance to psychological influence, and it is far harder to reach him with persuasion than an ordinary person.
The combination seems strange only at first glance. The Path of the Black Emperor works with someone else's order, and for that sometimes one is needed who cannot be argued down or broken — and the step's method of action says this directly.