Coilskar Cistern is a naga-run water-lined cave system located in northern Shadowmoon Valley. There is a very easy escort quest . You must kill the "boss" of this cave, Keeper of the Cistern, to unlock the escort. It should be noted that the shaman you are escorting, Earthmender Wilda is very tough, does a lot of damage, will heal herself, and will pickup a pack of water elementals along the way to help her. She is totally capable of soloing her own escort, it just takes a very long time. It should also be noted that if you do manage to fail the escort, her respawn timer is long.
There are a large number of Adamantite nodes in Coilskar Cistern, and makes a very nice looping run. Excellent for the miner who can stealth.