Modeus, like most of the Helltaker cast, is depicted as a short demon girl with pale skin, red irises, a black arrow-tipped tail, and silvery-white hair. Her hair is wavy and unruly, with several notable cowlicks of hair dispersed in no particular pattern. She has a left-swept fringe that stops at eyebrow's height, as well as two long segments of hair in front of either ear that drop down to chest-height, ending in a zigzag shape. While her irises are still red, rather than black pupils she has luminescent white pupils in the shape of hearts, and under her eyes is an always visible blush, though its intensity varies. Adorning her head are two simple black horns pointing up, as well as many small, red hearts that perpetually float around it.

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Modeus has a figure commonly associated with models or adult actresses, with a large bust, small waist, and wider hips. In her idle state, she appears with her hands resting on her chest, wearing a black blazer with a red turtleneck sweater underneath, a black pencil skirt split on both sides, red leggings and black high heeled boots Modeus at first appears to be the quintessential sex-crazed demon: upon first meeting her, she immediately demands that the Helltaker do her right then and there. She continues to exhibit hypersexual tendencies in the next level when the player asks for life advice, to which Modeus replies that they "skip all the puzzles, gather all the bitches and engage in proper harem activities", showing she is impatient for the completion of the harem. Pandemonica asks the Helltaker to forgive Modeus, and explains that most demons are like her because "lust for sin is in [their] blood" and that it is "hard to keep in check".

Modeus is shown to be very naive towards the more emotional aspects of love. When interacted with in the post-game level, she is shown reading a romantic comedy. She says she's never heard of romance before, but thinks it is "the kinkiest thing [she's] ever seen", and when asked about going on a date, she becomes flustered and calls the Helltaker a "perverted degenerate".

According to Azazel, Modeus craves for a romantic relationship but the concept terrifies her, prompting her to retreat into her unfulfilling sex addiction, which only has for effect to make her even more frustrated and thus angry