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 four-legged beast with 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.