D&D 5E Looking for suggestions: RP encounters in Hell

[Sezarious]

Seems to me that the current resident of Coldsteel Fortress might make a nice living off slave-trading, specifically planar-travelling mortals, and may even have a bounty out on such creatures. Perhaps one bounty hunter in particular has made itself famous tracking these mortals down and he resides in the fortress. He could make a powerful ally if he can be convinced to flip on his boss, but what could the PC's offer that the bounty hunter could use?

The bounty hunter might have a kill he wants to make, but can't due to other commitments or because without an alibi, it would too obviously be him. He can't outsource the work to devils, because demons and devils are able to protect the borders of their fortresses with impassable magic circles, however, mortals do not have to worry about such magics and can move past such protections with ease. The party would be perfect as they're not well known and they can handle themselves.

The hunter may even have a means of getting back to the mortal planes too, or have a contact who has.

 

[Delazar]

these are all very good, keep them coming!

 

[Trickster Spirit]

It's Dis rather than Stygia, but I've found plenty of Nine Hells inspiration to steal from in this thread.

 

[toucanbuzz]

A trapped, unarmed survivor of an adventuring group whose mind has been broken and body corrupted. He is convinced the party is more devils seeking to torture and trick him and is unlikely to listen to reason, though he knows one useful piece of information. As a being "touched by darkness," he is anathema to the inhabitants who leave him alone.