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
The mythic Relm of the Dead, located far underground (aka, Hades; Underworld)
Does Hades have a loose grip on the 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.