Great Helmet (5e Equipment)
From D&D Wiki
A large, often flat topped and cylindrical helmet popularized during the era of the Crusades. The helmet completely enclosed the head and could be worn over a chain coif as well as iron or steel skull caps. The far superior protection that the great helmet provides over other forms of head wear comes at a cost. The very narrow openings for the eyes creates a very restricted field of vision for the wearer, mostly eliminating peripheral vision.
You have disadvantage on Wisdom (Perception) checks while wearing a great helm.
Partial armor only grants its AC bonus if you are wearing light or no armor. If you are wearing only one piece of partial armor, you are still considered to be wearing your base armor type (e.g. no armor or light armor). If you are wearing two or three pieces of partial armor, you are considered to be wearing the heaviest type of partial armor worn (e.g. medium or heavy armor). You cannot wear four or more pieces of partial armor.
|Great Helm with Mantle, Wreath, and Ornaments|