FANFIC: Zaun Sewer Story part 1

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Surface tension breaks and a heavy drop of water tumbles onto Twitch's fur from the darkness abover. Repelled by layers of oil it simply rolls and tumbles down the creature, absorbing noxious compounds as it goes. As it somersaults away off his tail, the sewer cobbles smoke for minutes where it lands.
The Plague Rat himself, better things on his mind, scampers over under vaulted, crumbling archways, up corroding pipes and ancient, forgotten scaffolding. Zaun's vast and ancient labyrinth sewers speed past him and he runs, searching, sensing, scenting the air and snarling. Intruder! Intruder! In his realm! With his subjects! Oh but surface thieves and surface burglars, surface metal faces, oh how he will claw and tear.
Then, stopping on a dime, he stares into the dark. Sniffs the air, listens, feels soft currents of stale fog on his whiskers. Snarl and scamper forgotten he begins to creep, silent, deathly silent, clinging to the shadows he slides liquid like into a vast pipe, and through it, up and round and by, his rat's senses honed on a single, sensible trail. Out into a passage softly lit by luminescent mushrooms, vaulted in fine marble worn smooth by centuries of dripping water. A great canal flows placidly through, carrying the waste of the world above, this place is almost new. He's climbed high up, Twitch knows, and the surface isn't far. Surfacers come here, sometimes, to cross things off lists and kill whatever lives here. His jaw clenches, and, noiseless as a shadow, he dives into the filthy water, following the trail onward. Diving under a rusted grate he surfaces, and comes face to face with a great, bronzed door. Smooth like glass and utterly featureless, it's molded to the wall like it was cast there. No handle, no lock, no knocker. But the trail goes through it.
"Nnno no no NO NO!" he squeals, scratching his feet on the floor and stamping. Growling he throws his head around, whiskers probing the air and his nose huffing. Still wailing, he turns around and dives back in the water, under the grate and up again. Scampering out of the water again, he darts through the nearest sizeable copper pipe and begins the hunt anew.
Slowly, over hours, cursing, squeaking and scraping, he circles his prey. Through every pipe and crevice, around and around, he closes on the boundaries of his prey's nest, drawing a map with his senses. By process of elimination, the contours of the bronze door room emerge. It's sealed on every side, hidden behind thick rock and that damnable door. No holes, no cracks, no entry, until... finally! Through a narrow pipe and over some rubble, at the very back of the room, a single underwater canal sealed by a great bronzed grate. He tears and pushes at it, and it does not budge. He surfaces again, out of air, and screams curses at the dark. He floats there for a moment, rodent mind darting this way and that. Underwater, struggling with the grate, he had heard them screaming. He needs help.