Rift Quest:The Mousetrap  

Find Arthur's Lockbox up on the mountainside behind a big rock at 4546,5021 and try to open it. You will get a message that you need the key. Luckily Stillstep's Lackey shows up and attacks you. Kill him and he will drop Arthur's Key. Now you can open the box, get the Keystone, and take it to Adriana Weaver back in Granite Falls.