The Bone Helmet is the headpiece counterpart to the Bone Armor. Its intimidating visage appears to be the skull of a stag with an attached cloth hood.
Like the bone armor, the bone helmet takes all related slots of a player’s head equipment. As such, the bone helmet can’t pair with any other equipment worn over the mouth or eyes.
While the bone helmet provides a decent amount of projectile and melee protection, it suffers from a total lack of any cold or radiation resistance.
Without any cold or radiation resistance, you cannot safely wear the bone helmet to freezing biomes or more significant points of interest.
Despite the bone helmet and the bone armor technically consuming all of a player’s equipment slots, the combination only counts as wearing two armor pieces.
This technicality makes the armor combination safe from the Patrol Helicopter.