Ivan Glaziev is a supporting character and antagonist in the series, serving as a member of the Monroe Family, one of the major mafia organizations in the city of Ergastulum. He is a Caucasian man with brown hair and a large fringe that falls over his right eye, which he is sometimes seen keeping closed. Ivan typically wears a suit with the top buttons of his shirt left undone, and he is often characterized by an arrogant smirk on his face.

In terms of personality, Ivan is depicted as being deeply cruel, sadistic, and arrogant. He possesses a cocky and patronizing attitude towards other subordinates and treats his responsibilities within the mafia as if they were a game. He openly disdains underlings and complains that the Monroe Family coddles them. Most notably, Ivan holds an intense hatred for the Twilight population, which are humans with enhanced physical abilities but shortened lifespans due to a drug. He considers them to be monsters, despite the Monroe Family's comparatively sympathetic stance towards them, and is openly sadistic in his dealings with them.

His motivations stem from a deep-seated contempt for Twilights, driving him to orchestrate violence and purges against them. He is a mole who betrays the Monroe Family by secretly working for the rival Corsica Family. He passes information to Uranos Corsica, who gives him standing orders to find and kill the powerful Twilight Nicolas Brown whenever an opportunity arises. Ivan arranges violent attacks, such as the assault on the Cristiano Family, by blackmailing a B-level Twilight with the lives of his wife and daughter. In a display of his complete lack of morality, Ivan later reveals that despite the man's cooperation, he had already murdered the family by chopping off their limbs.

His actions are among the most heinous in the series, which has led to him being identified as a complete monster by critics. He is shown leading the persecution of Twilights, having them butchered and tortured, with his attacks not sparing innocent civilians or even children. Ivan also keeps the female Twilight Erika as his personal hitwoman, having conditioned her through years of mental and sexual abuse. He admits to a genuine thrill in raping her every evening, specifically because her face reminds him of her brother, Delico, who always greeted Ivan politely.

Ivan plays the role of a treacherous subordinate who escalates the conflict between the mafia families. His position within the Monroe Family gives him cover to carry out the Corsica Family's goals of destabilizing the city and eliminating Twilights. He maintains key relationships with his boss, Daniel Monroe, whom he betrays, and with his handler, Uranos Corsica. He also has a direct and abusive relationship with Erika, whom he uses as a weapon.

In terms of development, Ivan does not undergo a positive change or redemption arc. Instead, he is a consistently vicious antagonist whose treachery is gradually revealed to the audience. His primary ability lies not in physical combat, but in his cunning, manipulation, and strategic cruelty. He commands loyalty through blackmail and fear, and utilizes Twilight hunters like Erika and Mikhail to do his dirty work, orchestrating attacks from the shadows while his subordinates engage in direct combat.