Old Guard Faction Leader

Every faction have a leader and can be changeed.

Reformist: Ricter, Albin (If Ricter removed) ultin it take Sushel

Oligarch: Tusk, Marcel if helperd, Mikail if both of them arested, Edith if all of them arested

Old guard: Orso, Valken if Orso removed... but i swear i saw in my games Lileah or Heron take the spot

How do i change the old guard leader? What are the trigers?