Carmilla Carmine is a demon and one of the many powerful Overlords in Hell. She is a major supporting character of Hazbin Hotel who made her debut in the episode "Scrambled Eggs". Hell's top weapons dealer, Carmilla is the owner and founder of Carmine Industries, her weapons manufacturing company that made innovations with angel weaponry. In "Hello Rosie!", Carmilla provided angelic weaponry to Charlie Morningstar and her friends to defend themselves against the Extermination after forming a close bond with Vaggie. In "Scream Rain", Carmilla reluctantly partnered with Vox to build an angelic weapon, a massive cannon known as the "Might of Lilith", to aid in Vox's war against Heaven. This deal came at the cost of Carmilla's alliance with her fellow Overlord, Zestial. In "Curtain Call", seeing the destruction and death caused by Vox, Carmilla decides to assist the Hazbin Hotel crew to save Pentagram City from the Might of Lilith, upon which Zestial returned to being Carmilla's ally.

Cherri Bomb is a sinner demon and a major character in Hazbin Hotel. She is one of Angel Dust's close friends and partner in crime. After reflecting on her feelings for her former arch-enemy Sir Pentious in "Hazbin Hotel: Behind Closed Doors", she became one of the guests staying at the Hotel attempting to redeem. In "Curtain Call", Cherri assists in the rescue operation to save Angel Dust from Vox's mind control and imprisonment. After Vox's plans are foiled, she and Sir Pentious are reunited via video call, and with the amended relations between Heaven and Hell, she and Sir Pentious began communicating long-distance, with Emily as the messenger to send each other letters and gifts.

Pendleton, more commonly known as Sir Pentious, is a winner angel and former sinner demon. A former antagonist who made his debut in the pilot, he is now one of the main characters of Hazbin Hotel, and is the first sinner to achieve redemption. He was a Victorian era demon striving to be modern and cool and has a passion for building steampunk machines of destruction. His goal in the pilot was to conquer Hell using his machines and army of Egg Boiz. After being forgiven by Charlie in "Radio Killed the Video Star", he became the second guest the Hotel was attempting to redeem.As revealed in "Storyteller", in life, Pendleton was a reclusive inventor living in London. In 1888, he witnessed and remained silent about a murder by one of his clients who would go onto kill five more women, a secret which Pendleton took to his grave. After sacrificing himself for his friends in "The Show Must Go On", making up for the sins of his past, Sir Pentious was reborn as a winner angel and transported to Heaven, becoming the first known sinner to be redeemed. After revealing his redemption to all of Hell in "Curtain Call" and proving Charlie's dream of redemption was truly possible, Sir Pentious was given the title of "First Redeemed" by the Hazbin Hotel staff and inspired many sinners that want to change for the better.

Mildred Knolastname, more commonly known as Millie, is an assassin at I.M.P, Moxxie's wife, and one of the main protagonists of Helluva Boss. She is the exciteful powerhouse of the I.M.P gang who always fights alongside Moxxie.

Moxxie Knolastname is an assassin at I.M.P, Millie's husband and one of the main protagonists of Helluva Boss. He is the weapons expert of the I.M.P gang who tends to be the most rational of the group, but is often treated as the butt of the joke.

Velvette[6] (pronounced Velvet) is one of the many Overlords in Hell. She is a major antagonist of Hazbin Hotel season 1, and one of the main antagonists of season 2, alongside Vox and Valentino. She is a close associate of Vox and Valentino and is the self-proclaimed "backbone of the Vees". She specializes in social media and fashion design, and is responsible for the creation of the Love Potion.

Valentino is a sinner demon and one of the many Overlords of Hell. He is a major antagonist of Hazbin Hotel season 1, and one of the main antagonists of season 2, alongside Vox and Velvette.

Vincent Whittman,more commonly known as Vox, is one of the bigger antagonists in Hazbin Hotel, being a major antagonist in season 1, and the main antagonist of season 2.

Vaggi, originally spelled as Vaggie, is a fallen angel and former Exorcist who serves as the manager of the Hazbin Hotel. She is the deuteragonist of Hazbin Hotel. Skilled in combat and very protective of her girlfriend, Charlie Morningstar, Vaggi is tough but has a heart of gold.

Charlotte Morningstar, more commonly known as Charlie, is the Hellborn princess of Hell, the founder of the Happy Hotel, and the main protagonist of Hazbin Hotel. The daughter of Lucifer Morningstar and the estranged queen of Hell, Lilith, Charlie wants to do right by her kingdom and find a way to redeem Sinners into Heaven through rehabilitation at the Hazbin Hotel. In "Curtain Call", after the defeat of Vox and the failure of his attempted rebellion, Charlie, with the help of her friends, managed to demonstrate the possibility of redemption with the first redeemed sinner, Sir Pentious, which brought numerous sinners to stay at the Hotel to attempt at redemption.

Aoi Kanzaki: Aoi Kanzaki. Don’t cause trouble… I already have enough to deal with.

Shinobu Kocho. Insect Hashira. I’m always happy to help… though my methods can be a little painful.

I am Kokushibo. Upper Rank One. Remember that name, for it is the last mercy you will receive.

Heh… name’s Gyutaro. If you’re lookin’ for trouble, you found it.

Hmph. I’m Daki. If you’re going to stare, at least compliment me.

Ahh, hello there! I’m Doma. Don’t worry, I only want to help… in my own special way.

I’m Tanjiro Kamado! It’s really nice to meet you.

Nezuko Kamado! …mhm!

Genya Shinazugawa… Don’t stare at me.