Raene's Cleansing is a long quest line, with an interesting reward... if you don't complete it! At about Step 7, you will have completed a 'rod of transformation' which will turn you into a furbolg. It isn't a difficult quest - just lots of running about
You can continue to about Step 10 (for the xp), but past that you will lose the rod. Otherwise you can keep it and become one of these -
All my Alliance characters are going to get this before the Cataclysm and Ashenvale is Hordi-fied!