Book one of the Broken Earth trilogy, The Fifth Season, established a rich world with the unique characteristic of having a fifth season that occurs every so often in addition to the normal four. These seasons bring with them earthquakes, volcanic eruptions, and acid rain from ash-choked air and they last for many years. Humanity survives by adopting Seasonal Law, a harsh culling of society down to only those who provide a valuable services and skills, along with the magic of Orogenes that do their best to control the shakes and divert the forces of the land away from communities. Alabaster, a ten-ring Orogene, finally reveals at the end of the first book that Fulcrum teaching is all wrong and that trained Orogenes, like himself and Essun, are just treating the symptoms and not the cause. He now knows the cause of these fifth seasons and he has taken the first step to address it. Unfortunately his effort has altered him in such a way that he is now dying and no longer capable of going any further, so he asks Essun to take the next step in saving the planet. Is she willing to believe his mad theory and put aside her search for her daughter? And sign up for the same fate as him in the process?
The Obelisk Gate - the cause of the Broken Earth