Ionotatron. The Chronopticus Chronicles, #2

When a construction accident takes out the mayor of Mars' largest domed city, Pierce Steadman is elevated into the role. Tasked with overseeing the reconstruction of Magnopolis after the Great War, he sets out to separate the city from its Earth-inspired past and to restore hope to its population. Yet other forces also have designs on the city. As references to God disappear from the Network Archives, those forces unleash a towering destructive robot unlike any other: Ionotatron.