The Story of Nautilus
Nautilus was a diver working the deep sea outside of Bilgewater — one of the men who went down into the ocean's unmapped trenches looking for the sunken treasures and lost cargo that Bilgewater's salvage economy depended on. He was lowered into the deep by a crew that, when something grabbed him from below, cut the line rather than lose the winch mechanism. He was left to whatever had him. Whatever had him kept him.
He exists now inside a massive deep-sea diving suit, fused to it in ways that suggest the fusion is biological rather than mechanical. Something in the deep got into him and through him and around him, and what emerged was not the man who went down but something that carries his name and his memories and his specific, focused rage. He is enormous. He is slow. He drags an anchor chain that has become his weapon. He pulls things toward him — people, ships, anything that has the misfortune of being close when he decides to reach.
He comes from the sea to find the men who cut the line. Bilgewater is a port city with many people who have done things they'd prefer to leave in the water, and Nautilus is the reminder that the water remembers. He is not random in his violence — he is targeted in ways that suggest he still has enough of the man's memories to know who deserves to be found. The chain does not discriminate, but the hand on it does.