The One Beneath

There are legends and myths even among the supernatural communities.
Stories which explain the unexplainable and tales which defy the simple binary of confirmation or rebuttal. Many supernaturals, particularly those of high society which rely upon their knowledge of and power over the world to define their sense of self, discount these stories as the fiction of the uneducated or gullible and frequently enough they are proven correct in their denial, but there are some legends that are more true than anyone would hope them to be.
Deep in the darkest corners of the pacific ocean there is something no living being, supernatural or mortal, can comprehend. It has held countless monikers throughout the centuries, but these days is most popularly known in supernatural communities as The One Beneath. Its age and size are beyond comprehension, with some stories claiming it was already ancient when it arrived on in the newly created oceans of the Earth. Yet despite the efforts of both mortals to explore the ocean depths and supernaturals leveraging capabilities well beyond humanity no verifiable accounts of The One Beneath exist. Even elementals which live in the oceans have no concrete evidence of its existence.
Despite this, stories persist of ships sunken, aquatic beings taken, and entire island civilizations wiped out all by this creature of a scale unimaginable. And despite the protestations of the more grounded, the shared fear of the deep ocean unites almost all living beings.