About the conflict on Roshar. Radiant are returning to the world to fight the singers under Odium. The god Honor is dead, but another Cultivation is still alive doing who knows what. Odium is bound to the Rosharan system and wants to leave to destroy other worlds. Humans can bond spren to get super powers, but can die. Singers can get super powers without spren and also have Fused which can come back to life infinitely.