Divine Beast Leviathan

The Divine Beast Leviathan (リヴァイアサン) was a gigantic monster that was sealed away underneath the floating island Andika.

Appearance
The Leviathan was a gigantic serpentine-like creature at least 1 km long, with its head alone being 300 meters. It was covered in black metallic scales, with each of them the size of a tower shield, as well as being covered with dark red veins. Its mouth was filled with two layers of large razor-sharp fangs.

Similar to other ancient monsters, like the Devourer, the Leviathan did not possess a mana crystal within its body, but rather its whole body acted as one large mana crystal.

Personality
As a monster, the Leviathan was incapable of possessing complex emotions and was only able to act on its instincts that were considered too dangerous for it to roam about freely. It did, however, display an unyielding hatred towards Andika due to it having been the source of its imprisonment for thousands of years.

Background
The Leviathan was a monster that existed long ago during the age of gods on Tortus. Its power was so dangerous that the people prayed to the gods to protect them from it, to which they responded by sealing it away with a giant artifact in the form of an island that would be known as "Andika".

Chronology
The Leviathan's seal remained undisturbed for many centuries, until Andika's ruler Baharl Devault uncovered ruins deep below the island that included a shattered fresco depicting the history of the Leviathan, as well also being the key to releasing it once it was repaired. Baharl had his daughter Diene use her special magic "Renewal" to repair some of the fresco in the hopes of it telling him a way to control it for himself, in the hopes of using it against his enemies. As Diene spent more time restoring the fresco, Andika's weather and surrounding sea life became increasingly volatile, until Baharl eventually decided that it was too dangerous and suspended his efforts at researching it.

When Andika suffered an attack from both the Melusine Pirates and the Holy Church, the Leviathan was freed from its seal after Diene used her magic to restore the fresco while under the mental control of the apostle Ahat (who was acting on the orders of her master Ehit ). Once freed, it attempted to destroy Andika in anger for having been sealed under it for so long. Its efforts, however, were being thwarted by Miledi Reisen as she was using her gravity magic to keep Andika suspended above the water in order to protect the people living there. Her interference further angered he Leviathan and it unleashed a powerful magical jets of water from its mouth that killed many of the church's knights and nearly killed Miledi's companion Oscar Orcus while he was protecting her. It continued its attacks and had nearly pushed them to the brink of defeat, but was saved by Meiru Melusine, as she used her restoration magic to aid them. Oscar then engaged the templar knights, while Miledi and Meiru fought the Leviathan. Despite their best efforts, the two of them were unable to inflict much damage against the gigantic monster, and whatever damage they did manage to inflict was healed almost instantly afterwords. As they were running low on mana, Miledi came up with a plan after realizing that the Leviathan's scales were made of metal. As the Leviathan unleashed another ferocious elemental attack against Miledi, she managed to endure it long enough for Meiru to sneak up on its head an used her magic to reopen its previous wounds. Immediately afterwards, Oscar arrived after being teleported by his comrade Naiz and used his "Metamorph Chains" artifact to transmute the Leviathan's metal scales off of its head. That provided an opening for Miledi to unleash a powerful lighting attack with all the mana she had left, and defeated the beast in an incredible display of power.

Despite its defeat, the Leviathan's initial objective to sink Andika succeeded, but the citizens managed to evacuate to safety. Furthermore, the Leviathan had survived the battle and would eventually be taken by Ehit to reside within the Sanctuary, where it would be placed in is own habitat that was full of other monsters.

Thousands of years later, the Leviathan's domain was visited by Hajime Nagumo, Shea Haulia and Tio Klarus, while they were searching for Ehit in the Sanctuary. It hid below the water as it created a massive weather barrier that dulled their sense of direction and caused them to move around in a loop. Once Hajime discovered the cause of the disturbance, he deployed a series of powerful explosives, which caused the Leviathan to emerge from the water. It then immediately turned its attention towards Hajime's group, and was prepared to attack them with a massive burst of compressed water from its mouth. As it unleashed is attack, Hajime countered it using his railgun-enhanced sniper cannon "Schlagen Acht Acht". The cannon's bullet managed to cut right through the stream of water before it slammed into the Leviathan’s mouth. It punched right through the back of its throat, and pulverized the scales on the back of its head as it exited from the other side. It thrashed about in the ocean as it howled of pain, while a river of blood was spilling from its wound. Hajime then fired a second, more powerful shot at the monster. He intended to hit its head, but only hit its torso due to it thrashing around in pain. It let out another howl and sank beneath the ocean. It then began o suck up a bunch of seawater to plug up its wounds. As it healed most of its wounds, the Leviathan resurfaced and was prepared to attack Hajime once more, but it began to back dow down after sensing the intensity from Hajime's gaze towards it. That provided an opening for Hajime to attack once more with his rifle. The shot hit its torso once more, but the leviathan had shielded it by coiling its tail around the area. It was then prepared to unleash another water jet attack rom its mouth, but Hajime redirected it back with his "Orestes" portal artifact. However, The attack failed to inflict much damage on the monster. It soon managed to fully heal itself using the ocean water, but a second later, another part of its torso spontaneously exploded. This was caused by Hajime covertly inserting his spider-like "Arachae" golems through the openings of the monster's previous wounds, and then have them release massive quantities of burning tar from the Treasure Troves they each possessed. This combined with the seawater inside the Leviathan’s body caused a powerful steam explosion. As more water entered the monster through its new injuries, it caused a chain reaction that created more steam explosions, which left it writhing in pain again. Hajime sought to use this opening to kill it with his rifle, but he failed to inflict a fatal shot due o the monster constantly writhing around in pain. In a desperate act, the Leviathan attempted to save itself by tearing out a part of its tar-soaked flesh with its jaws, and spit it out with a water jet. Hajime and the others were prepared to engage the Leviathan while it was still vulnerable, but it grew even more terrified after seeing Hajime gaze at it once more, having finally realized that he was actually planning to eat it, and made a hasty retreat beneath the ocean. It then dispelled the storm it created, so as not to give Hajime a reason to pursue it.

The Leviathan would be killed soon after when the entire Sanctuary imploded thanks to Miledi.

Hajime Nagumo
Hajime was the first being to ever cause the Leviathan to experience fear. It was so scared of him that it sought to flee deep into its lair and never see him again.

Physical Abilities

 * Immense Physical Strength - The Leviathan had great strength in proportion with its size.
 * Immense Durability - The Leviathan's metallic scales were able to protect it from most attacks.

Magical Abilities

 * Immense Mana - The Leviathan possessed an overwhelming amount of mana that was able to produce massive shockwaves from its emission.
 * Weather Manipulation - The Leviathan was capable of generating massive storms through its very presence alone.

Skills

 * Mana Manipulation - It allows direct manipulation of mana without the need for magic circles or incantations.
 * Mana Discharge - It allows the user to focus and emit mana from their body.
 * Mana Conversion - It allows the user to convert mana into stat bonus for a certain period of time, thus allowing them to boost their own strength.
 * Healing Conversion - It converts mana to boost one's natural self-healing rate.

Trivia

 * In, the  was a primordial creature that was referenced several times in the as having been slain by God. In one iteration, it was actually regarded as a representation of God's powers.
 * The Leviathan is currently the largest known monster to have existed.