Who is Strewth from The Last Continent: A Discworld Novel and what is their importance?

Strewth is an opal miner in the outback of the last continent on Discworld, Fourecks, Strewth discovers something that gleams like frosty green fire. After a celebratory beer, Strewth and his coworkers unearth a hollow object whose walls are the thickness of a plate and that has tiny toes. It is The Luggage, which has followed protagonist Rincewind the Wizzard to this barren, arid land.