Shalltear Bloodfallen is a true vampire originally created by Peroroncino as an NPC in the game YGGDRASIL, guarding the first to third floors of the Great Tomb of Nazarick. Transported to a school environment in the Isekai Quartet crossover, her background and core traits persist within this new setting. She possesses a petite stature, appearing as a young girl with silver hair in a high ponytail, pale skin, and crimson-red eyes. Her typical attire is a gothic-style dress with a bonnet, capelet, and frills. Sensitive about her flat chest, she uses breast pads to create the illusion of a fuller figure, an insecurity affecting her interactions, especially with women possessing larger busts. Personality-wise, Shalltear is prideful, flirty, and openly expresses her sexual preferences, including necrophilia and sadomasochism, often discomforting others. She maintains fierce loyalty and a romantic obsession toward Ainz Ooal Gown, frequently fantasizing about him. This devotion fuels her direct rivalry with Albedo, another guardian competing for Ainz's affections. Their dynamic shifts between collaboration and conflict, though they unite regarding Ainz. While arrogant, Shalltear adheres to school rules in the crossover and is less disdainful toward humans, interacting more civilly with classmates. In Isekai Quartet, Roswaal L. Mathers serves as her homeroom teacher. He assigns her to work as a class nurse alongside Rem, forcing collaboration despite Shalltear's envy of Rem's physique. This jealousy resurfaces when Rem is cast as the prince in a Cinderella play, a role Shalltear desired for Ainz. Shalltear also holds a grudge against Aqua after Aqua mocks her use of breast pads, leading to an attack halted by Albedo's intervention. Though her combat abilities as a vampire, like blood manipulation and resurrection items, are part of her lore, they remain background elements in Isekai Quartet's school narrative. Her character development emphasizes adapting to mundane tasks and social dynamics while her core traits of loyalty, pride, and rivalry endure.