The Leviathan is one of the Five Terrors created by to war in the Above. When the War in the Above was lost, cast the Leviathan down to Gaiga so it could bring as much annihilation as possible which it did until it was defeated, captured and sealed by ♆.

The Leviathan is a serpent-like creature from which's body six more serpents spread. From these serpents, even three more serpents emerge. These serpents all have eight tentacles like octopi do at the place where their heads should be placed. All the ends of the tentacles have a round mouth and six rows of teeth all as long as a twohanded sword. In the center of the mouth, an eye is located that has an orange sclera, seven black rings on the bloodred iris and a green pupil. The Leviathan and its extremities themselves are completely black, except the suction cups, which can glow in a dark green manner. The main mouth of the Leviathan is located where you'd expect it from a serpent and has nine rows of teeth and the eye that lies within the center has nine black rings, its sclera is white, the iris is red and the pupil black.

The Leviathan was born by Tiamat, earthborn daughter of the spaceborn , hidden from the others after corrupted her mind. The LeViAtHaN was taken by to 's realm and there it was one of the Five Terrors that clashed with the spaceborn during the War of Chaos and when everything fell apart were sent to Gaiga to rage as long as they could.

The Leviathan was defeated by ♆, after the War in the Above was lost for . decided to cast the Five Terrors from its realm and they were transported to Gaiga. So did also the Leviathan land in Gaiga's oceans and in desperate attempt to spread the last possible chaos, terrorized the ocean's inhabitants, who realized they were powerless against this ancient evil. It was in the hour of deepest desperation, that came down from its oceanic planet after the Spaceborn collectively sealed and riding on a meteor crashed into the Leviathan. When the Leviathan was paralyzed due to the crash, took its mighty fisher's net and captured the Leviathan. Then the two took a dive under the ocean's surface and found an underwater cave in which opened up a gateway to the Below, then imprisoned the Leviathan there and span the net across the cave's entrance and reascended to the surface, leaving Gaiga and returning to the Above where it reentered its palace.

The Leviathan is the most dangerous creature that ever entered the ocean of Gaiga. It is able to literally steal the light away from the ocean, no matter the depth of it. So it can be, that even a little under the surface of the oceans you traverse pure poisonous darkness. If you are very unlucky, in the still uncleaned areas of the ocean, you might even be transported between dimensions. Furthermore, the poison of the Leviathan caused some of the oceanborn spirits to be corrupted and some of them were even used in the War of Wrath.

The Leviathan was later given the title, "Terror from the south".