Hades meaning “the underworld” and not referring to the greek mythology. I believe also referred to as Sheol. It refers to just “the common grave of man” and not specifically “hell” as often depicted.

Basically, “everyone comes back from the dead.” A lot of this section has flowery prose for over describing everything. “Graves and death give up their dead” is basically just “the dead come back to live so they can be judged” (which just further illustrates that nothing happens when you are dead, because you have to be resurrected just to be judged)