This mask belonged to an ancient sage of dragon lore, who turned from worship of Tiamat to worship of an unknown deity of evil knowledge.  While wearing this mask, you gain extra spell slots based on your character level.  At 18th level, you gain an extra 7th-level spell slot; at 19th level, you gain an extra 8th level spell slot; and at 20th level, you gain an extra 9th level spell slot.  At 18th level or above, you can cast 1st level spells at will.  In addition, no matter what level you are, you gain a +1 bonus to AC.

Notes: Bonus: Armor Class, This is based on Miraak, the dragon priest mask from TES V: Skyrim (the Dragonborn expansion). The original enchantment reads: Increases your Magicka by 40-70 points (based on level)., dragonborn that can cast spells and is at least 18th level, Buff, Utility, Headwear