Host is a major antagonist from the spin-off series focusing on Megumin. He is a high-ranking demon who serves as the loyal right-hand man to a dark god named Wolbach. As a demon of significant power, Host is sent on a mission to the Crimson Demon village to unseal his master, who had been imprisoned there. It is during this task that his path crosses with the young Crimson Demon girl, Komekko, Megumin's younger sister.

In terms of appearance, Host is an imposing figure. He possesses a tall and muscular build with pitch-black skin that often has a metallic sheen. His face is marked by white eyes without pupils, and he has two pairs of horns: one set sprouting from the sides of his head and another protruding from his cheeks. Large, bat-like wings extend from his back, granting him the ability of flight, and his mouth is filled with sharp teeth.

Host's personality is defined by a fascinating duality. On the surface, he is intimidating, prideful, and possesses an aggressive demeanor that frightens most people, including Megumin and Yunyun upon their first encounter. However, beneath this fearsome exterior lies a surprisingly friendly and honorable nature. He is fiercely loyal to Wolbach, viewing the contracts he makes as absolute and serving his master with total devotion. This sense of duty drives his actions and makes him a formidable agent of Wolbach's will.

Despite his demonic status, Host proves to have a soft spot, particularly for Komekko. The young girl manages to touch his heart during their meetings in the graveyard, leading to an unlikely friendship. He is so moved by her that he promises to become her familiar if she ever successfully summons him in the future. This shows a well-behaved and almost gentle side that contrasts sharply with his monstrous appearance. He is also true to his word and resilient in the face of absurdity, often bewildered but accepting of his fate when dealing with the eccentric inhabitants of Axel.

Host's primary motivation throughout the story is the fulfillment of his duty to Wolbach. He travels to Axel in pursuit of her, intent on completing their contract and serving his master. His search brings him into direct conflict with Megumin and her party, as he believes the cat Chomusuke, who is always with her, is connected to Wolbach. While his goal puts him in opposition to the protagonists, it is not born of pure malice but from a sense of demonic obligation and loyalty.

As a high-ranking demon, Host possesses immense strength and magical power. His physical prowess is demonstrated by his ability to defeat an entire adventurer party with a single punch. He is confirmed to be stronger than another demon named Arnes, and his power is said to be comparable to that of a general in the Demon King's army. He has high magic resistance and normally claims he could survive a direct hit from Megumin's signature Explosion spell when at full strength. In addition to his physical might and resilience, he can also cast advanced forms of offensive magic, including a powerful fire spell called Inferno that creates a massive blaze.

Host's development within the story involves a shift from a purely threatening antagonist to a more nuanced figure. He begins as a terrifying unknown entity in the forest, but his interactions with Komekko and his honorable conduct in the face of Megumin's relentless tactics reveal his depth. His story arc culminates in accepting his defeat after a series of exhausting encounters, acknowledging that his contract with Wolbach might be at an end, and humorously lamenting his potential future of being "ministered to" by Komekko. This resolution highlights his loyalty, his resilience, and the absurdly chaotic world he has found himself in.