Leviathan is a hulking man with bleach white skin, black markings on his face and forearms, and a single row of brown spikes running down his spine. He has a relatively small head, with beady orange-yellow eyes and a wide set of teeth. On Leviathan's fingers and toes are wavy red claws. There is also a set of "tubes" with the same appearance stemming from is back and connecting to his head. He wears torn black plants with a brown belt.
Helical Size (ヘリカルサイズ Herikarusaizu?): Leviathan's Quirk allows him to create powerful, twisted streams of water from the red appendages on his fingers and head. These streams of water can pierce through things like a drill and have a wide range of attack.
- Leviathan's black and white color scheme, coupled with his muscular frame and "tubes" snaking on his body, makes him resemble the DC villain Bane.
- His white skin color and wide smile also make him resemble The Joker.
- Leviathan's Japanase voice actor, Shogo Sakata, also voices Enma Kannagi.
- Leviathan is referred to as the Rampage Villain (暴走ヴィラン Bōsō viran?).