In whose power is it solely within to allow passage out of the underworld? Whose rule are the subjects in the Underworld under? Is #1 or #2 not Hades?
Underworld
Hades alone can allow passage out of the Underworld. Hades created a terribly difficult task for Orpheus to complete to bring Eurydice from the Underworld.  The subjects of Hades in the Underworld are under his complete control.
The mythic Relm of the Dead, located far underground (aka, Hades; Underworld)
Does Hades have a loose grip on the Underworld?