Bring Gerenzo Wrenchwhistle's Mechanical Arm to Ziz Fizziks in the Stonetalon Mountains.
I met Gerenzo once, but let me tell you, he's not easy on the eyes. His flesh looks like it's rotting away, and he's grafted metal and gears onto his body, replaced some of his limbs with mechanical ones.
Northeast of here, far above Cragpool Lake, up near the water wheel is where Gerenzo watches over the entire site. There's no way I could fight my way up there, not to mention take on Gerenzo... But you look like you might be able to make it.
If you kill him for me, I'll make it worth your while!