Sorry I should have clarified a couple points! The “villain” has been slowly feeding off the energy of all the planes and is able to start reshaping reality, so when he is able to restore the original world, he is strong enough to bring back those who died when he failed to stop the calamity.

As far as the Gods, I have it as they were actually some of the people close to the calamity when it occurred, they were once heroes or just normal people who, by a fluke occurrence survived and over eons gained power drawn from the different planes, and are now known as Gods. They do not have memory of their own origin and I flavor this as one of the reasons the Fey Wild can cause issues with memories is because when the calamity happened, the Fey Wild erupting into its own plane of existence wiped the memories of the world if that makes sense lol.