One idea could be exploring Lucifer's past before the events of Hazbin Hotel. Maybe show his rise to power and the decisions that led him to become the ruler of Hell. Another could be a story where Lucifer has to deal with a new, powerful demon who challenges his authority in Hell. A third idea might be a fanfiction that focuses on Lucifer's relationships with the other main characters in a more in - depth way, like his true feelings towards Charlie and how he views her plan for the hotel.
One idea could be that Lucifer decides to test Charlie's determination to redeem sinners in a series of extreme challenges. He might create artificial situations where it seems impossible for a sinner to be redeemed, just to see if Charlie will stick to her beliefs.
One idea could be exploring Lucifer's past before ruling Hell in the Hazbin Hotel universe. Maybe his rise to power, his relationships with other powerful entities at that time.
One plot idea could be Lucifer seeing a different side of Adam that no one else has. Maybe Adam shows kindness towards a lower - class demon, which makes Lucifer question his own views. Another could be that they team up to solve a mystery in Hell that threatens both the sinners and the native demons. And a third idea is that Adam tries to introduce Lucifer to more 'human' concepts like forgiveness, which Lucifer initially resists but gradually comes to understand.
A possible plot could involve Lucifer dealing with the physical and emotional changes that come with pregnancy. This might include her struggling to maintain her usual image of power while also experiencing the more vulnerable aspects of carrying a child. Additionally, it could explore how her relationship with other important characters, like Charlie, is affected as she goes through this new phase.
One idea could be Adam's backstory exploration. Maybe he had a different life before coming to the Hazbin Hotel universe and that could be delved into. For example, his family, his upbringing, and how those things might have shaped his current self.
One idea could be an OC who is a fallen angel trying to redeem themselves in the Hazbin Hotel. They could face challenges from both the sinners and the hotel staff, adding an interesting dynamic.
One idea could be that God decides to visit the Hazbin Hotel to see if there's any hope for redemption among the demons. He could interact with Charlie and the other characters, causing them to question their beliefs and actions. Another could be a story where God sends an angel to the hotel undercover to observe and report back, and the angel ends up befriending some of the demons, blurring the lines between good and evil.
Well, a plot idea could be that Alastor discovers a new power within himself in the context of a fanfiction. This new power could either help or hinder his standing in Hell. Also, perhaps a plot where Alastor tries to start his own 'radio show' in Hell that's different from his usual broadcasts, and it causes all kinds of uproar among the demons. Or, what if Alastor is forced to team up with someone he really dislikes, like Vox, to face a common threat to their power in Hell?
One idea could be a story where Lucifer and Alastor have to team up to deal with a new threat to Hell. Maybe a powerful demon from another realm is trying to take over, and they have to put aside their differences. They could start off not trusting each other much, but as they face challenges together, they begin to respect one another's abilities.
You could also write a fanfiction about a new character arriving at the Hazbin Hotel. This new character could have a unique power or a very different personality from the existing ones, which would create all sorts of new interactions and storylines. Maybe they have a special ability to see the pasts of the other characters and use that to help them on their path to redemption.