The Watchman is a partial incarnation of the Old GodAtar which the Bahutha creates on a tri-centennial basis in order to communicate with their dormant deity.
Background & Involvement
A wisp of Atar's consciousness possesses a baby in utero and corrupts the vessel throughout the span of its childhood until it is an abominable reflection of his darkness: this is the creation process of a new Watchman.
At the beginnings of human civilization, Atar grew with so much power that it became too much to contain. His sphere of madness encompassed the nation he had built around him, causing his Bahut kin to become useless as servants, and his physical body to wither. In order to contain this effect, he commanded his children build and encase him in a massive dome-like temple called the Abscess. In the Abscess, Atar could no longer communicate with the Bahutha, and so he separated part of his consciousness to possess one of the Bahut's unborn. This child grew to become the first Watchman.
Since Atar is normally too powerful to be contained in any capacity, when a Watchman nears death, Atar will choose from the Bahutha's pregnant and command them to relinquish their baby. This is because the assimilation of Atar's consciousness into a vessel must begin prenatally. A regular human body would reject the possession completely, but an unborn baby may be corrupted in the womb and born as an abomination suited for the task. The creation of a new Watchman occurs every three centuries, around the time in which a vessel would become completely sapped of its life force.
Walker Madison's child is chosen to be the newest Watchman during the events of Dead in Desert Bleak.