Hardhead is a namedSkeleton Miner enemy that was originally intended to be located on Crux Prime. For unknown reasons, Hardhead, along with Blackmarrow, was removed from Crux Prime before the world was added into the game. Despite this, Hardhead remains in the game's coding, and can be spawned by a Mythran and fought.
Hardhead was spawned by a Mythran in Nimbus Plaza on January 3, 2012.
Hardhead, unlike other named Skullkin (except for Blackmarrow), does not appear in the Ninjago storyline.