Once favored by Asmodeus, Zariel sided against him in the Reckoning of Hell. She was overthrown when Bel, the leader of her military forces, turned against her and sided with Asmodeus. Bel was installed as Lord of the First in her stead.
Zariel reclaimed her title as Lord of Avernus following Bel's demotion by Asmodeus. Bel fell out of favor with the Archduke, and was forced to serve as Zariel's advisor.