I'm looking for ideas for my campaign PC going to Hell

[Throne12]

So I starting a campaign back up. I'm looking for ideas and advice.

The party are level 11 with a paladin, wizard and ?, and a monk jumping in here and there. The party is tasked by one of the three god to recover the paladin love Interest/God's daughter's soul. This will stop her from spreading a plague that is killing some people and turning others into devils & Demons. So I want the party to go up to lv15 while in hell. Hell has both devils and demons in it. Devils live in cities and demons roam the wilds.

So any encounters ideas would be nice and any advice.

[Unoriginal]

So I starting a campaign back up. I'm looking for ideas and advice.

The party are level 11 with a paladin, wizard and ?, and a monk jumping in here and there. The party is tasked by one of the three god to recover the paladin love Interest/God's daughter's soul. This will stop her from spreading a plague that is killing some people and turning others into devils & Demons. So I want the party to go up to lv15 while in hell. Hell has both devils and demons in it. Devils live in cities and demons roam the wilds.

So any encounters ideas would be nice and any advice.

So just to make clear, this is not the D&D Nine Hells?

[Throne12]

So just to make clear, this is not the D&D Nine Hells?

No my cosmology is different I don't have a after life souls are created or reincarnated. There is a realm where the God of creation and she turns chosen souls into Celestials reside in. this is where souls are born. There is a war between celestials and fiends over this realm. Because the fiends want pure souls.

Hell is a large plain were there are nine cities that is ran by the 8 devil princes. They are part of a kingdom where the 9th city is ran by the king of Hell. The Great Demons are powerful bings the roam the wilds outside the cities.

[Unoriginal]

No my cosmology is different I don't have a after life souls are created or reincarnated. There is a realm where the God of creation and she turns chosen souls into Celestials reside in. this is where souls are born. There is a war between celestials and fiends over this realm. Because the fiends want pure souls.

Hell is a large plain were there are nine cities that is ran by the 8 devil princes. They are part of a kingdom where the 9th city is ran by the king of Hell. The Great Demons are powerful bings the roam the wilds outside the cities.

Well reading this makes me think of this campaign ideas:

A trickster-style entity has something the devils and demons want (artifact, information, prisoner of interest, etc), and has set up a large competition/tournament/games with the something as the prize.

The catch is, despite being set in Hell, only mortals (as in, non-Outsiders) are allowed to participate.

So now the various powers are either recruiting mortals, trying to prevent mortals from participating, or otherwise trying to sabotage or influence the games for their own reasons (including "is not happy the entity is using Hell and making it look like the fiends can be manipulated").

Enters the PCs, who can get involved in many ways.