The Warden of Heaven is the head of a counter-Bazian Ark which falsely claims special associations with the mystery of the Mathic world. The Ark is a heretical offshoot of the Samblites. The Samblites supplement their faith with the notebooks of Saunt Bly who while not a Deolater identify with his struggle for the truth. The Warden of Heaven claims that Saunt Bly was a Deolater who found a proof of the existence of God and was Thrown Back because of it.
The religion is powerful enough that when an expedition is sent to meet the Daban Urnud, and they indicate that one Emissary can be sent, the Warden is selected.
Upon arrival on the Daban Urnud, the Warden insists that he remove his space suit. However, as the air on the ship uses a slightly different physics, it is very difficult to breathe. The Warden succumbs and an aneurism bursts. He dies, and his body is returned without comment via the ship's nuclear explosive chute. The crew find him to be a fool and break off contact, though they continue their spying and infiltration efforts on Arbre.
According to Sammann, "They threw the Warden of Heaven out of the airlock" became the hip catch phrase of the moment when speely footage of the expedition goes public.