Leviathan is a very envious person that does not take no for an answer. He hates company and whenever he does show himself he is rude and cold. Whenever somebody else has something that he wants he will experience intense jealousy and usually challenge the person in question to a potentially deadly battle.
Even so, he's not always bad, and he is actually decent to his own Pieces. Overall, however, he is an unpredictable and violent person that is best left alone. Good thing he prefers to be in waters that are as deep as possible.
Leviathan is fairly tall, but nothing too big compared to other Demon Lords. That is not to say he won't stand out though. Leviathan's skin is a pronounced blue, he has fin-like ears that match his skin tone, his feet are similar to those of a duck, being webbed together, and the same is true for his hands. His wings look like those of a winged fish and for tails he has two mermaid-esque tails coming from his lower back. His eyes sport dark blue sclera and yellow irises, and his mouth is wide and sharp, with equally sharp teeth to boot. At the end of his fingers and toes (if you can call them that) he has sharp claws, and he has spikes running along his back. His hair is wild and long, hanging far down his back, with wavy streaks of green hair that resemble seaweed.
Leviathan usually wears very little to prevent water resistance, resorting to just undergarments usually.
- Leviathan's first name, Cutulum, is derived from the Lovecraftian monster Cthulhu.
- The name of Leviathan's trident, Lotan, was a sea monster bearing many similarities to Leviathan in real mythology.
- Out of all the Demon Lords, it is no question that Leviathan's usual form is the least human.
- Leviathan was killed and later had his position replaced by Astaroth, something that infuriates Leviathan to no end.
- Out of the original seven Demon Lords, Leviathan and Asmodeus are the only two that are of more than one species.
- When not in the water, Leviathan will usually have his two mermaid-esque tails coiled around eachother for convenience, as he claims they take up too much space. He is envious of Asmodeus' slim tails, although they would not aid him well in the water.
- Much like Satan, Leviathan wears very little clothing. Even so they still don't get along well.