The Mine Shaft is located on Raven's Cove. It will take you to the upper area of Raven's Cove. This area includes, El Patron's Mine and El Patron's Ship. When on the upper area of Raven's Cove, there are also Fire Bats that can be defeated. You cannot gain access to the shaft until a key is found. This Key is found as part of the Raven's Cove Story Quest that can be done at level 30.