Concrete Mandible/IF-1667

===Background===
The following accounts can be traced to a single leather-bound journal originally found in a locked wooden chest alongside a sextant-like device of indeterminate origin and a shell that matches no known species of mollusc. The chest was located in a storage room in the Legscraper’s lower levels that was described as “smelling faintly of the sea”. Subsequent attempts to locate and navigate to said room have been unsuccessful thus far. The journal details the exploits of the crew of a large sailing vessel, The Tokyo Adrift, descriptions of which are largely consistent with mid-17th century galleons.
===With The Tokyo Adrift===
To assist in naval combat, Captain Strongbody had The Tokyo Adrift outfitted with a naval ram. Strongbody had hoped that the figurehead would come to be feared as a symbol of the Adrift, warding off potential marauders from a distance. Sketches of the initial design resemble the modern day proteus or olm. Unlike most figureheads of the age, Mandible appears to have been carved from stone, likely to boost their hardiness and damage potential. It did, however, come as a surprise to both captain and crew when the figurehead arrived as a sentient elemental, capable of limited communication and motility.
Unfortunately, Mandible was far less useful in practice than in theory. Over the course of one summer in 1666, they had the lowest known rate of successful rams. Another sailor had described this as "the worst hitting season ever seen, possibly in history”. Despite expressing an interest in performing their intended role, the added weight made the ship unwieldy and incapable of the tight manoeuvrability that had allowed for much of its early success. As the journal states, “it soon became clear that Concrete would be more useful to the Adrift off it, rather than fastened to its bow”.
This began a period of deep research and chasing rumours. The crew of the Adrift were chiefly searching for a location “oft quoted in tall tales by fools and romantics”, the . Described as a bay with “rocky shores dappled with tide pools, their perfectly still surfaces reflecting the grandeur of the sky above”, rumours said the pools were populated by all manner of bioluminescent flora and fauna. Populations of “sea stars and anemones glittered below the surface”, with “glowing chitons zipping back and forth like shooting stars”. If the stories were to be believed, sailing through the bay of the Wishing Pools on the night of the new moon with a sizeable contribution of coin would allow a sailor to will their heart's desire into existence. 
After several dead ends, the Adrift tracked down the Wishing Pools and used their power to grant full life to Mandible. Unwrapping themself from the bow, Mandible slithered into the Immateria Sea, unfurling to their full length for the first time. Snout to tail tip, Mandible was roughly the length of the ship.
While they enjoyed several years with the crew, in the spring of 1666, Mandible reported feeling “a deep and primal call” and that “it was their time”. Following this, Mandible would dive into the Depths, a seemingly extradimensional space located at a depth of at least 2000 fathoms. This would mark the last sighting of Mandible by the crew, making them one of the few crew members who would not be present for the events of 1667.