Summary
(Leviathan is a two-headed piscine demoness with a dichotomy in her anatomy: her humanoid body is divided into two, indicated by the left half of her body appearing white and the right half of her body indigo. Both heads share lengthy fin-like white hair styled in a mohawk. However, the left head is more humanoid, has webbed ears and electric blue eyes with black sclera and cyan eyeshadow, while the right is more animalistic, has a longer neck, pupilless seafoam green eyes, and a fanged, eel-like snout. In addition, the left head's hair has faint pink streaks on it with a black strip and violet gradient interior; the right head's hair is bioluminescent, with black streaks on the topside, a dark violet-cyan gradient interior, and green spots scattered across. Leviathan wears a sleeveless high-collar black crop top with a diamond-shaped cutout and twin downward-facing swirls, the right swirl being violet and the left swirl lavender. She wears a black skirt featuring a semicircle-patterned rim bearing the same color split as the swirls. She also wears elbow-length gloves; black on the left and white on the right. Each head wears a light cyan pearl necklace with only the left head wearing pearl earrings, and has a cyan belt to match.) (Personality While the full extent of her personality has yet to be revealed, Leviathan's two heads appear to have independent personalities. The right head is more cynical and more in charge, while the left head appears to be relaxed and composed. The left head was even friendly to Mammon, unlike the right, and got mad when the right head moved them away from him. The relationship of the two heads is further indicated when Mammon invited Leviathan out after Blitzo's trial; the right head showed active annoyance at Mammon and attempted to ignore him, but her left head seemed to genuinely enjoy being around him, and looked hopefully at the right head, indicating that she hoped that she would allow them to take up Mammon's offer. It is unknown if she shares the same views of superiority as the other deadly sins do. However, she does recognize Satan as her leader and "the law" of Hell.)
While brief, in "Mastermind", Mammon shows an interest towards Leviathan, asking her if she would like to go out with him after trial. While she has not said anything positive or negative about him, the left head seems to reciprocate the interest, however the right does not.
As shown in "New Pentious", Lucifer keeps pictures of Leviathan in his room at the Hazbin Hotel, showing a presumed fondness for his fellow Sin. In "Silenced", Lucifer has received a large luxurious handbag from Leviathan alongside gifts from other Sins and Mammon's bribe for him to come back.
Her hair can glow, even in dark environments.
As a Deadly Sin, Leviathan is presumably immortal and only able to be killed by angelic weaponry.