Abaddon an 10,000-year-old demon Prince of the Underworld possessing the body of a 1700s Puritan boy. He appears as a small child in 18th-century attire—a gray doublet with white collar, brown breeches, and tights Chaotic but Child-like: Despite being an ancient entity designed to wreak havoc, Abaddon has adopted the mannerisms of the child whose body he inhabits, appearing innocent, curious, and sometimes naive. Internal Conflict: He deeply despises being trapped in his current, weak vessel and often struggles to reconcile his past power with his present limitations. Delusional Optimism: He believes Hell will eventually come to rescue him, even though his former realm has forgotten him and replaced his castle with an acid pit. Relationship with the Freeling Family: Throughout the series, Abaddon grows attached to his "adoptive" family, particularly Esther, often protecting them despite his claims that he only views them as acquaintances. Ineptitude with Modernity: He is unfamiliar with modern technology, finding things like vacuums and computers challenging, and is terrified of wooden wind chimes. Immortal & Trapped: An ancient demon from Hell, bound to a human body after a failed exorcism, leaving him unable to return home. Personality: Boastful about his past power but often acts like a petulant child, prone to tantrums and complaining. Humanity: Despite being a demon, he develops affection and enjoys simple human things, leading to an internal conflict about his identity. Background: A High Prince of the Black Realm, he's been in the boy's body for over 300 years at the Undervale hotel.