Head on down the slope and talk to Fisk. He's the darker-skinned Shadow, and if this is your first time in the area he'll introduce himself to you when you reach him. Ask about the ornamental sword and agree to pay 110 Ore; if you don't have the extra 10 Ore go back to Whistler and ask for it. Do not mention Whistler was only going to pay 100 Ore as this will result in Fisk refusing to sell it to you. Once you have the sword head back to Whistler and ask for the 10 Ore (if you didn't already) and then hand him his sword. He will be very pleased and promises to put in a good word for you.
Unless you are planning to rip him off, return the sword right away- otherwise after a few days he will become hostile to you and make this quest impossible to accomplish.