Without the existence of the powerful and almighty apostles, it was truly impossible for the war to come to an end any time soon.
As such, the mortals or those that did not possess any combat abilities were left to suffer from the ravages of the unceasing war that occurred covertly and overtly.
Furthermore, according to the foundational laws established when their world was created, once an apostle ascends, they would no longer be bound by the mortal world, meaning they wouldn't be able to return unless they sacrifice part of their divinity or limit themselves by sealing their strength.
Thus, even if the apostles wanted to return to save their kin, they wouldn't do so recklessly. This was because they wouldn't dare risk their lives by limiting their strength just to come to the mortal world.
Unless the apostles were beyond the absolute control of the laws, if they died with their strength limited, they would truly die.
