"Find the first enchanted skeleton" is an objective in the quest The Bloody Harvest in TK Bahas Bloody Harvest DLC
The Vault Hunter now needs to search the Necropolis to find Enchanted Skeletons in order to forge a key for the Mystic Lock that has appear on the gate to the Pumpkin Kingpin.
There are 3 marked search areas. In each you will find Boarded Up Crypts. Smash them in to either reveal the Enchanted Skeleton you are looking for or a horde of reanimated bandits.
The first skeleton can be found directly to the East of the gate that The Pumpkin Kingpin locked.