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. Appearance Moxxie is an imp with red skin and white freckles on his cheeks. His white pointy hair leads up to his curvy black and white striped horns. He also has yellow sclera with black slit pupils. He has a long red thin tail with a quadrilateral barb at the end, as well as lanky digitigrade legs ending in what appears to be cloven red hooves, reminiscent of artiodactyls. Moxxie's usual outfit consists of a navy-black coat with red buttons and white cuffs, black pants a white shirt that has a black turtleneck, a large red bow-tie, and fingerless gloves. Personality Moxxie is the I.M.P's weapon specialist; and as such, has a vast knowledge of weapons and often brings a variety of them along during jobs. He is often the most vocal and realistic of the employees regarding the company as a whole despite its dysfunctional environment, and is bullied consequently. Despite being a murder-for-hire imp, it seems Moxxie is queasy with unnecessary killing beyond their targets, and uncomfortable with the idea of killing targets who have families, and attempts to give people second chances, as seen in "Murder Family".

Mildred Knolastname,[11][12] 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. Appearance Millie is a short imp with red skin and a rather petite, pear-shaped figure with a long devilish tail. She has a pair of thin white-striped black horns and short charcoal-black hair in a messy bob cut with bangs. Her eyes have yellow sclera and long, thick eyelashes protruding from them, with a small beauty mark under the right eye. Her front teeth have a gap as well. She also has a black heart tattooed on her right shoulder, and makeup which consists of shimmering dark red eyeshadow, thick black mascara, and black lipstick on her lips. She also has two white spots on her upper right arm, two on her lower left arm, two white streaks on her upper left and lower right legs, two white spots on her tail, and one on the tip of her tail. Millie's attire is all-black with a tint of yellow, which consists of a black choker around her neck, a black cold-shoulder, slightly midriff-baring crop top with the straps being held by two golden-yellow buttons, black fingerless gloves, high-waist black torn denim pants and black toeless footwear, which exposes her hoof-like toes.

Blitzo Buckzo[1] (pronounced Blitz) is the founder and manager of I.M.P and is the main protagonist of Helluva Boss. He is the adoptive father of Loona and a former co-worker and best friend of Fizzarolli during their days as kids in the former's father's circus. Appearance Blitzo is quite tall for his species, though estimates himself as being roughly four feet tall,[10] and sports a harlequin-like aesthetic. He has red skin with white burn marks of various sizes that cover parts of his forearms, chest, and his tail, as well as most of the right side of his face. His irises are red and he has a heart-shaped skull symbol on the center of his forehead. Blitzo has fairly broad forearms and hands, and a long narrow head, out of which extends large, curved, black and white striped horns. He has black spines on his head and upper back, as well as on his tail. His tail ends with a triangular point that has a black spot at the tip. He has pointed feet with boot-like heels which are shown to have black on the heels and toe areas. As shown in "The Full Moon", Blitzo has red gums. Blitzo wears a tattered slate gray collared coat with red buttons down the breast, black knee-high boots matching the shape of his feet, and elbow-length black fingerless gloves featuring large, rounded yellow decorations on the upper side of them. In "The Full Moon", the yellow decoration on his left glove is infused with his own Asmodean Crystal. Blitzo also wears a red skull charm around his neck.

Loona is the hellhound receptionist of I.M.P, the adoptive daughter of Blitzo, and one of the main protagonists of Helluva Boss. On rare occasions, she joins the rest of I.M.P during their missions on Earth. Following "Sinsmas", both Loona and Stolas are the receptionists of I.M.P. Appearance Loona is a hellhound with a wolf-like appearance. She has a pointed, dog-like muzzle with sharp and pointy teeth, and a black nose. Her eyes have bright red sclera, white irises, and slit-like pupils. Her fur is white with grey countershading encircling her face, grey patches on her shoulders, and long, hip-length, voluminous silver hair swept to the side to reveal her dark grey ears; one of which is pierced with two small, black hoop-piercings, while the other is ragged. She has a large and long, dark grey bushy tail with white on the underside. She also has a piercing on her right eyebrow with a black hoop for jewelry. Her outfit features a big, spiked black choker-collar around her neck. Her tattered grey, off the shoulder crop top is held up at the neckline by a series of crisscross spaghetti straps that form an inverted pentagram.