|Romaji||'Shiro' no Rivuaiasan|
|Light Novel Debut||Volume 1|
|Manga Debut||Chapter 5|
|Anime Debut||Episode 2|
Leviathan is described as a large creature covered by a white outer shell, with a giant horn on its head and rows of sharp teeth. It also shares some common characteristics with marine mammals, having front flippers, tail fins and an air hole on its back, leading to speculation by scientists that it might have mutated from a blue whale.
At an unidentified point in the past, Leviathan inherited the Authority of 'Silver' Tiamat, transforming into its current form as a result. When the Dragons reemerged into the modern world 25 years before the events of the story, Leviathan was among them. A year before the start of the series, Leviathan passed by a ship where Iris Freyja and her family were on board and sank it, with Iris being the lone survivor and awakening her powers as a D as a result.
In Volume 1, Leviathan marked Iris Freyja as its mate and launched an attack on Midgard in order to retrieve her. It shrugged off the attacks from NIFL's forces by using its repulsive field and easily approached Midgard's defense lines. Although it was intercepted by the Counter-Dragon Squad led by Mitsuki Mononobe, it succeeded in tearing apart most of the defensive lines by launching a powerful repulsive blast. Any further attacks by the Counter-Dragon Squad were rendered ineffective, since Leviathan would either create spatial discontinuities to slice off parts that were poisoned by the Ds or would repulse any normal attack. It was even able to defend itself against Iris' explosions and Yuu Mononobe's Anti-Dragon Armament, Marduk, albeit with some injuries. However, Yuu made another contract with 'Green' Yggdrasil, supplementing Marduk with additional data, which allowed him to form its main cannon, Babel. With this new weapon, along with support from the Counter-Dragon Squad, Yuu finally succeeded in destroying Leviathan. Following its destruction, its Authority was passed down to Yuu.
Powers and AbilitiesEdit
Anti-gravity: Leviathan's Authority, Code Vier, grants it the power of anti-gravity. With it, Leviathan can hover by neutralizing gravity, generate repulsive fields that can reflect incoming attacks or blast away objects, and can even sever things by creating a spatial discontinuity between two repulsive fields.
Marking: Like most Dragons, Leviathan can mark a suitable D as its mate, transforming her into the same type as it upon contact.
- Leviathan's name originates from the sea monster with the same name that appears in the Old Testament.