This category is reserved for helmets that originally affected a warframe's stats; one stat increase in exchange for one stat penalty. Starting from Hotfix 13.2.3, these helmets became no longer available from the Market or as a reward from Alerts, and "statless" variants, which are available today, replaced them. Arcane Helmets that existed before this change were kept intact and can be traded between players.
Arcane Enhancements were implemented to fill the role initially meant for these helmets, but cannot be applied to them.
A summary of Arcane Helmets can be found below;