What an unusual and accomplished tale! I love the backstory you have made for Filius here (I think there has been much debate in fandom as to whether he has goblin blood, so making him half-goblin is a very reasonable idea), and his uncomfortable, violently-erotic relationship with Griphook seems just right. Neville, too, is forthright and true to character; he is justly proud of the sword. Some lines I particularly loved:
"It's as though you took my father's skull and mounted it upon the wall like a trophy, and when I politely asked for it back—" His lip curls. "—you refused, as you might someday need it for an ash tray." Ouch. That really puts the goblins' position into focus; it makes a lot of sense.
"When I first saw you, I thought you were unbearably beautiful..." "When I first saw you, I thought you looked like a half-melted candlestick," Ha! So funny - I love the little touches of humour throughout this piece. I also love the fact that Filius' attractions are firmly rooted in his goblin side, even though he lives the rest of his life as a wizard.
"I couldn't keep my money under my mattress anymore," Te he :-)
The beauty of a man may bring pleasure for an hour, but the beauty of a blade is eternal. His work done, Griphook turns to go, and lifts a hand to wipe the water from his eyes. Oooh, ambiguous ending FTW! Is Griphook sorry to have used Filius in this way, or is he just pleased to have the sword? This one will keep us guessing.
An inspired piece, Mystery Author! This one will stay in my thoughts for a long time.