The Leviathan's Palace

History

Discovery

Roughly fifty years ago, a fishing expedition operating off of one of the westernmost islands of The Jaws discovered something while they were out at sea. While casting their nets as they usually would, the bottom of their boat bumped against something underwater; an object large enough to cause the vessel to stop in its tracks and turn hard to starboard. The crew of the ship were baffled by this, and could at first could not see what the ship had caught upon. Then, the light changed, and they saw something beneath the waves. Just a scant few metres beneath the surface was what looked like a stone platform, upon which a network of what seemed to be roots grew in a great tangled mass. It was this which the boat had sailed into.
One of them got out of the boat and dived beneath the surface to inspect the platform. Now that they were underwater, they were able to witness the full extent of the structure. The platform was connected to a stone spire that descended into the deep along with the roots. A few metres down, the spire started to grow strange, bulb-like protuberances that glowed like lanterns, illuminating a small space around them. As he followed the roots down with his eyes, it was only then that he saw it: An enormous structure the size of a hold, entirely covered in glowing flowers and roots. It stretched out for what he thought to be miles in every direction, and disappeared down into the void further than he could estimate.
The ship and its crew rushed home to tell their families of what they had discovered. Of course, no one believed a word of it, and the underwater structure would be left undisturbed for another decade. It was only when, by coincidence, a second ship beached itself upon the platform - this one containing a Deveer, who was studying the fish in the region for inspiration - that the rest of the mainland finally started to take notice. An expedition was sent out to ascertain the truth of these claims, headed by the Deveer who had been in the fishing boat. This time, a full examination of the structure revealed it to have an entry point, roughly twenty metres under the surface.
The Deveer took it upon himself to swim down and investigate, aided by a device he had created to allow him to hold his breath for longer while underwater. He made his way over to the entrance, and there found something strange; another type of plant, this one consisting of what appeared to be a lattice of seaweed-like vines. Curiously, he reached out and touched the plant. Before he could react, the mesh pulled apart at the centre, sucking in a great plume of water and him along with it. For a moment, he was disoriented, unsure of which way was up and which was down. The sensation persisted for almost a full minute, during which time he could do nothing but hold his breath, before suddenly he found that the sensation of water upon his limbs had disappeared. Opening his eyes, he found himself inside of a small stone room covered in grates, and dripping water water everywhere. The inside of the building, it seemed, somehow contained air. In front of him was a staircase, leading deeper into the structure.
After a moment's hesitation, he took a deep breath, and began to descend.

Exploration

The Deveer who had first stepped foot within the underwater structure returned to his vessel after a scant few hours; much to the surprise of his crew, who had thought him long dead by that point. He informed them of what he had seen: Much of the inside of the structure was kept dry by a series of plants which served as a sort of 'stopgap' between the water outside, and the interior of the structure. When one made their way through the first layer of vines, they would enter into a room enclosed by such growths on the other side, where the water would begin draining down through a series of grates in the floor. Once it had done so, the vines on the other side of the room would open, and allow passage through them. The purpose of this system seemed to be to prevent the inside of the structure from flooding, and it had the side-effect of allowing humans to explore the inside without the limitations imposed by needing to hold their breath. For as well, though the Deveer himself could not yet explain from whence it came, the passages therein were filled with breathable air.
It was not long before a second expedition came to the underwater structure, spurred on by the tales of the first group. These men came prepared, and brought with them food and supplies for a prolonged exploration; covering them in water-proof packaging and bringing them with them inside of the structure. They delved far deeper than before, and it was there that they came upon something remarkable. In a flooded part of the structure which they had entered through another floral airlock, the entire wall was covered in all manner of bizarre, rock-like creatures. Bright red, blue, purple or green, they were unlike anything the divers had ever seen. And among them were all sorts of strange seacreatures; almost impossible to describe by their appearance, seeming something like cacti with hundreds of little tentacles protruding from them.
This discovery was exactly what the expedition had been hoping for. They pried from the wall a number of the corals and the strange sea creatures, and took them back to the mainland, where they sold them as exotic curiosities wrested from the domain of the deep. No one had ever seen anything like what they had brought back, and so demand for more was steep. But the most significant discovery came when one artisan realised that trace amounts of purple dye could be extracted from the fluids of one of the creatures brought back. It had been impossible to create purple dye up until then, and so this discovery triggered a flood of sea-delvers to descend upon the structure, eager to make a fortune.

Exploitation

It did not take long for the upper reaches of the structure to be stripped of their valuables. Hundreds of men carrying excavation tools scurried about the stone passages like rats, carrying backpacks laden with corals and polyps. Ever lustful for further treasure, they continued pushing deeper, having to set up increasingly complex supply lines and outposts to cope with the multiple layers of gates they needed to pass through. By this point, accidents had begun happening with what ought to have been alarming frequency, with men being poisoned, failing to surface in time, or simply just getting lost on their way back. But the allure of profit was too great for these concerns to be taken seriously, and so they continued onwards.
Divers had now made it to around the 80 metre mark. Here, the structure began spread out greatly in all directions, already-large passageways becoming even taller and wider. As well, to the explorers' initial terror, they discovered entire sections of passageway which appeared to have no walls, yet were not flooded. Upon further examination, they realised that the usual stone had been replaced with some form of strong glass in these locations, able to withstand the water pressure without breaking. These sections tended to overlook 'outdoor' areas filled with illuminating growths, from which entire schools of fish, coral, and other such creatures could be seen.
Around the time that the divers breached the 100 metre mark, expeditions deeper into the structure ceased entirely. Within a week of this occurring, roughly 2/3rds of those currently working at the structure abruptly returned to the mainland. Those who did so did not bring with them the expected riches, the majority returning empty handed. Instead, they spoke of a gargantuan creature they had witnessed in the depths, invariably being described as the size of or bigger than a castle. Stories differed as to the specifics of its appearance, with some saying that its bore the body of a fish and was covered in poisonous spikes, others stating that it appeared like an enormous eel with a flail on its backside, and others still that it was like an entire school of sharks merged together. No consensus could be reached on the beast's appearance, but all among the divers swore that it was real.
In light of these tales, interest in the submerged structure began to dwindle significantly. Fewer and fewer individuals were willing to head out to it, regardless of the potential wealth to be gained, and soon only a few fearless divers continued to make expeditions out to it.
Some came to believe that the creature the divers had spoken of was none other than the legendary Leviathan; a creature spoken of in the folklore of fishing villages throughout The Jaws, spoken of as part monster and part deity in equal measure. It was from this superstition that the structure finally gained its name, coming to be referred to as the Leviathan's Palace.