Escape the Underworld plot help

I’m DMing my first campaign (5 people including me who have never played DnD before) and I accidentally TPKed my party. Instead of ending it, I set them up with an escape from hell plot as the session ended, but I don’t think I know enough about official DnD lore to run this. I did have some ideas going in though.

1) Ghosts from their past, obviously. 2) They are currently level 2, and I plan to have them level up once or twice over a few sessions. 3) A strong monster that they probably won’t be able to beat, but it’s right by the River Lethe so they can push it in and convince it that they are friends maybe (like Iaeptus/Bob from Percy Jackson iykyk). 4) The final fight is a mirror fight because their souls were split but idk why they’d be split yet

Any advice or tips would be appreciated

Greetings SGB905,

If you are looking for good lore on the Nine Hells, there are a few books I'd suggest, but don't know if you have access to them:

• 2024 DMG: Has a decent section on the Nine Hells, including a description of each level, Infernal Hierarchy, and a few paragraphs on Nine Hells Adventures.
• 2014 DMG: Has the descriptions of the levels of the Nine Hells.
• M: Tome of Foes: Has an entire chapter on the Blood War, which goes deep into the Lore of the Nine Hells, the Devils that rule each level, and the full makeup of each level.

Hope that helps :)