At the age of 16, Meti enlisted in the third legion of the Middle Army, possibly related to Au Vam and the Yellow City. The symbol on Maya's back and Incubus' chair is a reference to the Middle Army. This is the Chinese character for "middle" (中).
At some point, Maya took control of the army, but lost it due to her life choices. Incubus took command without truly earning the rank, something that he has been mocked for.
Incubus is lord of the Golden Army, and his worlds are brutal anarchy, with what little of value there picked apart by the bloody warlords he hand raised from the remnants of the most powerful army in the universe. Taking into account the symbol on his chair, the Golden Army is likely the remnants of the Middle Army.