Behemoth

The is a giant beast that resides in the Demon Realm. It is said that when it's active, it swallows all life in its sight and seem to possess a portal to Camelot's dimension on it's back.

Appearance
According to depictions, the Behemoth is a four-legged beast with a dragon-like head and two very long straight horns. On its back are mountain-like structures. It is depicted to be several times larger than the Demon King, who in his own right was gigantic.

History
Long ago, the Behemoth woke up from it's slumber due to the Demon King exacting his furious justice upon rebellious vassals, it started to cause destruction in the Demon Realm, consuming all life in it's path, but the Demon King eventually managed to force the beast back into it's deep sleep with his massive force.

After the Demon King was defeated by the Seven Deadly Sins in the new Holy War, a "sea change" was caused, which woke up the Behemoth again to spread disaster across the Demon Realm once more. During it's path of chaos, it's evil force was released across every inch of the land, felling the Demon Realm's plants, animals and even the Demons themselves.

Around the same time, a young boy named Percival arrived in the Demon Realm and was taken care of by the current Demon king and queen, Zeldris and Gelda, he was shown to be capable of giving Demons affected by the Beast's evil force, their life back, from that moment on, being seen as a saviour by the Demon Clan. Not too long after that, the Behemoth's energy reached Zeldris' castle, but it managed to push the beast's energy back for now. One day though, Percival disappeared from the castle and in some unknown way, managed to put the gigantic Behemoth back into it's deep sleep, saving the Demon Realm.