Maybe Hades is the location that God Mode takes place in, often times called purgatory and the underworld. It is unknown if Hades is hell it self or Purgatory in witch souls wait for the fate to be decide before they enter hell, or heaven. In some of the Monsters bios in game they refer to Hades as a place and as a person himself.
Hades may also refer to the God Hades, who is kinda like Satan and runs the underworld. If that is true then the location of God Mode takes place in the underworld and Hades is the Ruler.