One frequent theme is his relationships with other characters. For example, his interactions with the main characters like Charlie or Alastor can be a central part of the story. Also, the theme of self - discovery is there. As he navigates the hotel, he might learn more about himself and his place in this afterlife world. And there's often the theme of chaos, given the nature of the Hazbin Hotel setting.
One great Sir Pentious fanfiction is 'The Adventures of Sir Pentious in Hazbin Hotel'. It delves into his attempts to assert his dominance in the hotel's chaotic world. Another is 'Sir Pentious and the Mysterious Guest' which has an interesting plot where he has to deal with an unexpected arrival.
There's a fanfic called 'Clash of the Demons'. In this, alastor and sir pentious are forced to work together on a task in Hell. Their interactions are filled with witty banter and a slow - building understanding of each other.
You can start by looking on Archive of Our Own (AO3). It has a large collection of fanfiction, and there are likely to be many stories featuring alastor and sir pentious there.
One common theme is his ambition. Many fanfics explore how far he'll go to achieve his goals of domination. For example, in some fics he'll make elaborate plans to take over parts of Hell.
Sure, there is. However, its distribution and accessibility might vary depending on the region and the platform. Sometimes, it could be a limited release or exclusive to certain comic conventions.
One interesting Sir Pentious fanfiction could be about his attempts to expand his territory in a more comical way. Maybe he tries to claim a small patch of land that's already occupied by some harmless critters and the chaos that ensues.
One idea could be that the characters from Hazbin Hotel end up in Paris where the Miraculous Ladybug story takes place. They could interact with Ladybug and Chat Noir, and maybe some of the chaotic energy from Hazbin Hotel causes trouble for the heroes as they try to keep the city safe. For example, Angel Dust might accidentally cause a distraction during an akuma attack.
One possible plot could be that the Doom Slayer somehow ends up in the Hazbin Hotel universe. He might initially be seen as a threat due to his violent nature. But then, they realize he could be an asset in dealing with some of the more dangerous demons in the Hazbin Hotel world. For example, he could help Charlie and her crew deal with some of the more unruly and powerful demons that are causing trouble in and around the hotel.