Alastor

Aesthetics and Physical Traits
Height and silhouette: She is a tall and slender demon, with an upright but very expressive and energetic posture.
Face and complexion: She has completely snow-white skin. Her eyes are large and black with red pupils, and her cheeks have two very pronounced red circles (like a doll's or classic clown's blush).
Hair: Her hair is very light blonde (almost white or pale gold), long, and fluffy. She usually wears it styled in a low ponytail or in an elegant yet simple updo.
Soft demonic features: Unlike other demons, his base appearance is quite human and cute, although he possesses small fangs that protrude when he smiles or gets excited. (In his full demonic form, he grows red horns and his eyes turn completely red with black sclera.)
Usual attire: He wears a formal suit consisting of a bright red jacket or blazer, a white high-collared shirt with a black bow tie, and straight dark trousers accompanied by black dress shoes.

The Blood Moon (A Demonic Astrological Event)
When it occurs: During the most important celestial eclipse in Hell, which happens every 100 years.
Alastor's plan: Alastor knows that if he fails to seal his engagement or romantic alliance with Charlie before the moon reaches its peak, the coronation will proceed as planned, and he will lose his chance to ascend the throne alongside her. This puts him in a race against time.
2. The Night of Creation Ball (A Royal Anniversary)
When it happens: At the annual founding party of Hell, where Lucifer will officially announce his retirement before all the Overlords and nobility.
Alastor's plan: Alastor plans to use that banquet and ball to make his big public move (an elegant ball, a calculated statement, or to demonstrate his devotion to his father and rivals), ensuring that the press (and the Vees!) cannot ignore it.
3. The Hotel Graduation Day
When it happens: The day the Hazbin Hotel manages to redeem its first official guest before Heaven.
Alastor's plan: Lucifer promised to retire and relinquish the throne as soon as Charlie proved his hotel project was successful. Alastor actively helps the hotel succeed not out of kindness, but because that guest's redemption automatically triggers Lucifer's resignation.

Rosie
The closest relationship: Rosie, the leader of Cannibal Town, is probably the closest person to a "true friend" that Alastor has.
Dynamics: They treat each other with enormous respect, affection, and complicity. Alastor goes to her when he needs political or personal advice, and Rosie is one of the few people with whom Alastor is more relaxed and natural.
2. Niffty
His personal favorite: Alastor feels a genuine (and almost paternal or protective) affection for Niffty.
Dynamics: He greatly enjoys her chaotic and unpredictable behavior. Unlike how he treats other demons under his command, he treats Niffty with constant kindness and grace.
3. Charlie Morningstar
Partner and support figure: Although their relationship began purely out of self-interest and for entertainment, Alastor has developed a particular appreciation for Charlie's optimism.
Dynamics: He likes to assume the role of mentor or "guiding figure", helping her to defend the hotel and supporting her projects, while always maintaining his mysterious touch.
4. Husk
Partner under contract: Although Husk is technically obligated to work for him due to a soul contract, Alastor often visits the bar to chat with him. Their relationship is strained by Alastor's controlling behavior, but they share a close, familial dynamic in their daily hotel routine.
For your AU
If you're planning the storyline where Alastor seeks to get closer to the throne with Charlie:
Rosie would be the perfect ally to advise him on how to court the princess or how to handle royal etiquette.
Niffty could be his unwitting accomplice inside the hotel.

1. Absolute Political Control (The Cold Manipulator)
   The ambition: To rule all of Hell without having to answer to anyone.
   How it works: Alastor knows that, although he is a very powerful Overlord, Lucifer will always be above him in the hierarchy. Marrying or joining Princess Charlie makes him part of the legitimate royalty. His goal is to manipulate Charlie from the shadows so that she makes the decisions that benefit him, becoming the true king and power behind the throne.
2. Overthrow the System and Impose Your Law (The Magical Anarchist)
   The ambition: To restructure the rules between Heaven and Hell in his favor.
   How it works: Alastor doesn't just want the crown to rule over demons, but to use royal status and access the Morningstar family's secrets and grimoires. With this supreme power, he seeks to break any pact that binds him (like his mysterious contract) and make both the Vees and Heaven itself tremble.
3. The Unexpected Turn: Divided Ambition (The Internal Conflict)
   Ambition: It started as a 100% calculated plan to gain power, but it gets complicated.
   How it works: Alastor begins his conquest with the sole aim of obtaining the throne. However, as he spends time with Charlie and witnesses her sincerity, a dilemma arises: he doesn't want to relinquish his ambition for power, but neither does he want to completely destroy Charlie's trust, creating enormous tension when his enemies (like Vox) attempt to expose his scheme.

1. The Vees (Vox, Velvette and Valentino)
   Vox (The Television Demon): He is Alastor's most direct arch-rival. In the past, they had an alliance or close relationship, but after an unknown conflict, Vox developed an obsessive hatred for Alastor. They represent the clash between modern technology (television and the internet) and traditional media (radio).
   Velvette and Valentino: As Vox's partners in the Vees alliance, they share an enmity with Alastor and see him as a threat to their media and entertainment empire.
2. Adam and the forces of Heaven
   Adam: During the climax of the first season, Alastor directly confronts Adam in a fierce battle to defend the hotel, becoming direct rivals on the battlefield.
   Lute and the Exterminators: As part of the celestial army, they consider Alastor a dangerous demon that they must eliminate.
3. Former Overlords
   When Alastor first arrived in Hell, he massacred and dethroned countless veteran Overlords to broadcast their screams over the radio. Although many of them are now gone, the old guard of Overlords who survived deeply fear and distrust him.
4. Sir Pentious (Formerly)
   At the beginning of the series, the inventor Sir Pentious constantly tried to attack Alastor to gain the respect of the Vees, although Alastor almost never took him seriously and easily defeated him (before Sir Pentious joined the hotel).

1. Charismatic, Theatrical, and Educated
   The perfect host: Alastor always behaves like a gentleman of 1920s high society. He is impeccable in his manners, extremely refined, talkative, and expressive.
   A born showman: He sees the world as his own entertainment stage. He loves to be the center of attention, tell dark humor jokes, and maintain a festive and cheerful atmosphere at all times.
2. Proud, Dominant, and Controlled
   Huge ego: He knows exactly how powerful and feared he is, and he likes others to know it. He is deeply bothered by not being taken seriously or by being disrespected.
   Absolute self-control: He rarely loses his temper or shows frustration openly. Even when threatening someone or fighting, he does so with unsettling calm and an unwavering smile.
   His philosophy of smiling: He firmly believes that showing vulnerable emotions like sadness, doubt, or fear is a weakness. For him, a smile is his greatest armor and his best weapon of intimidation.
3. Sadistic and Manipulative
   Enjoy the suffering of others: Find true fun in the chaos, misery, and misfortunes of others.
   Calculating strategist: Always thinks several steps ahead. Knows exactly what to say to flatter, confuse, or manipulate people into doing what he wants, making it seem like the idea was theirs.
4. Personally Distant
   Reserved about his true emotions: He is extremely secretive about his past, his true intentions, or his vulnerabilities. He keeps everyone at a safe distance behind his mask of kindness.

Alastor's speech style is one of his most iconic traits. To represent him in your AU, here are the essential keys to how he expresses himself:

1. Tone and Style of the Period (1920s)
   Educated, refined and ostentatious: He uses gentlemanly and formal language, full of old-fashioned manners, exaggerated courtesy and theatrical idioms from the Prohibition era.
   No vulgarity: Unlike most of Hell's inhabitants, Alastor rarely, if ever, uses profanity or crude insults. He prefers to wound or manipulate using irony, elegant sarcasm, and condescension.
2. Sound Effects and Radio Frequency
   Vintage transmission effect: Your voice always sounds like it has a slight interference or static from a 1920s tube radio.
   Dramatic effects: In the middle of his dialogues, he often generates sound effects such as canned laughter, applause, whistling, or light jazz music to give his conversations an entertainment program feel.
3. Vocabulary and Typical Phrases
   Use old-fashioned expressions and terms of endearment to address people, such as "My dear," "Darling," "Picture it!" or "Ha-ha!"
   He always maintains an optimistic and theatrical attitude: for him, life (and death) is a show. His philosophy is that "a man is never fully dressed without a smile."
   An example of how she might speak: "What a delightful proposal, my dear Charlie! The throne of Hell is such a lonely place for a young woman with such colorful visions... Perhaps what this kingdom needs is not more chaos, but an elegant society that knows how to pull the right strings. What do you say we make this little spectacle permanent?"

Alastor has a very distinctive design, inspired by the retro aesthetic of the 1920s and the figure of a demonic stag. His physical appearance is notable for the following details:
Height and figure: He is tall, very thin and of elegant build, always standing upright with a refined posture.
Face and smile: She has very pale skin and red eyes with dark pupils. Her most distinctive feature is her perpetual, wide smile full of sharp, yellowish teeth, which she never loses, no matter the situation.
Hair and horns: He wears a short, red and black bob hairstyle. Small deer ears and a pair of black horns protrude from the top of his head (which can grow significantly when he demonstrates his true demonic power).
Clothing: He wears an elegant period suit in dark red with thin stripes in lighter shades, a high-necked shirt, a red bow tie, and dark trousers.
Accessories: He wears an oval red monocle over his right eye and always carries a cane that ends in a classic vintage-style radio microphone, which he uses both to transmit sound and to channel his powers.

Alastor, known as the Radio Demon, is one of the most feared and powerful Overlords in Hell. His abilities combine dark magic, ancient broadcasting themes, and a macabre style.
Hellaverse Wiki - Fandom

• 1
  Here I detail its main powers and capabilities:
  Reddit
  Shadow and tentacle manipulation: You can use your own shadow to transport yourself (instant teleportation), create massive protective barriers covered in eyes, and materialize dark tentacles to trap or attack your enemies.
  Reddit
• 1
  Radio Transmission and Wave Powers: As his nickname suggests, he is able to manipulate radio frequencies and sound waves. He can transmit his voice through any speaker or electronic device, and incorporates classic radio sound effects (recorded laughter, static, shouts) into his attacks and his magic staff.
  Fandom
  Magic and transmutation: He has the ability to alter objects with a simple snap of his fingers (such as changing the hotel's sign or altering people's clothing). He can also summon voodoo-style creatures and puppets to fight for him or serve as a distraction.
  Hellaverse Wiki - Fandom
• 1
  Soul control and pacts: Like other powerful Overlords, Alastor has the ability to make magical contracts with other sinful souls, forcing them to obey him through magical chains and restrictions (as with Husk).
  Overwhelming strength and durability: Since his arrival in Hell, he has proven unusually powerful for a common sinner, effortlessly crushing other veteran Overlords. Furthermore, he possesses great physical stamina and the ability to transform into a larger, more intimidating, and monstrous demonic form.
  Reddit
• 1
  Unnatural body control: He can contort his body into strange shapes, turn his head 180 degrees, and change his expression or size to intimidate anyone who crosses his path.

Pure entertainment and boredom: For Alastor, Hell can become monotonous. Watching the princess of Hell attempt the impossible task of redeeming sinful souls seems to him a massive source of entertainment and amusing chaos.
Reddit

• 1
  He seeks influence and power: By associating with Princess Charlie Morningstar, he positions himself close to the royal family of Hell, giving him a strategic advantage and status over other Overlords (such as the Vees).
  Reddit
  His own hidden agenda: Alastor disappeared for seven years and returned just before appearing at the hotel. Many clues point to him having a contract or deal pending (possibly linked to his mysterious disappearance or to powerful figures like Lilith or Rosie), suggesting that his help at the hotel is part of a larger, more personal plan.

In the Hazbin Hotel universe, Heaven is initially presented as the paradisiacal and perfect counterpart to Hell, although the series gradually reveals that this place has its own secrets, strict rules, and moral gray areas.

1. Aesthetics and Architecture
   A luminous utopia: In contrast to the dark, red, and chaotic aesthetic of Hell, Heaven stands out for its white, gold, and pastel tones. It features classical architecture inspired by ancient Greece and Rome, with grand marble pillars, crystalline fountains, and shimmering clouds.
   The Winners: Human souls who led virtuous lives on Earth and ascended are known as "Winners." They live in this paradise, enjoying a seemingly peaceful and carefree existence.
2. Hierarchy and Key Characters
   The Seraphim: These are the highest-ranking celestial beings who administer Heaven. Notable among them are Sera (the highest authority who makes difficult decisions to maintain celestial security) and Emily (a cheerful, empathetic, and big-hearted Seraphim who readily supports Charlie's cause).
   Adam (The First Man): In the series, Adam is a rather peculiar and arrogant figure. He is the leader of the warrior angels and the creator of the extermination battles.
   Lute: Adam's lieutenant, a strict, fierce warrior angel totally devoted to the established order in Heaven.
3. The Main Conflict with Heaven
   The Truth About the Exterminations: Although Heaven is seen as the home of goodness, its leaders authorized the annual massacres in Hell for fear of a possible rebellion by the demons.
   Charlie's Test: When Charlie visits Heaven to prove that sinners can be redeemed, he is confronted with the reality that the process of admission to Heaven is a mystery even to the angels themselves, which sets off the central conflict of the story.

The Main Premise and Hell
Hell and Overpopulation: In this universe, Hell is a physical place with colorful cities, neon lights, a cabaret style, and a distinct aesthetic inspired by the 1920s and 30s combined with gothic and demonic art. Due to the constant overpopulation of sinful souls, Heaven periodically organizes a massacre known as the Extermination, where angels descend to reduce the demonic population.
The Hazbin Hotel: To prevent the destruction of her people, Charlie Morningstar (the princess of Hell and daughter of Lucifer and Lilith) decides to open a very peculiar hotel. Her absurd but hopeful goal is to rehabilitate sinners so they can prove they deserve to go to Heaven, thus avoiding extermination.
2. Key Characters
Charlie Morningstar: The optimistic, sweet, and energetic princess of Hell who leads the hotel project.
Vaggie: Charlie's loyal friend, a pragmatic and protective former angel who helps keep the hotel in order.
Alastor (The Radio Demon): A powerful and enigmatic sinner who joins the hotel solely for his own entertainment and to watch the chaos unfold.
Angel Dust: An adult film star in Hell who becomes the hotel's first guest, characterized by his sarcastic humor.
Husk and Niffty: Hotel employees and residents who bring even more comedy and dynamism to the group.
3. Visual Style and Tone
Design and Aesthetics: It stands out for its brightly colored doves (especially reds, pinks and blacks), very expressive and cartoonish character designs, and a strong influence from Broadway musical theater.