Orc Lord ascendancy
The Orcs only acknowledge authority born out of power and strength. As the current Lord of the Orcs ages and is perceived to be showing signs of weakness, challengers begin to come to the surface. Most of these are warlords or leaders of mines and even occasionally military leaders sworn to the currently leader perform cues.
Once the challenge is made there is a formal call to battle. The leader usually will fight the challenger however, frequently subterfuge is used and the challenger’s disappearance is never questioned.