This mask is the burial mask of an ancient king who worshipped Tiamat.  While wearing this mask, any abjuration or evocation spells you can cast you can cast as if they were one level lower.  For example, fireball is a 3rd-level spell.  With this mask, you could cast it with a 2nd-level spell slot (and still have it do full damage).  Likewise, you could cast fireball with a 3rd-level slot and it would count as a 4th-level slot.  However, you cannot cast a 1st-level spell as a cantrip.  In addition, you gain a +2 bonus to all spell attack and damage rolls and to your spell save DC.  You also gain a +2 bonus to AC.

Notes: Bonus: Spell Attacks, Bonus: Spell Save DC, Bonus: Armor Class, This is based on Nahkriin, the dragon priest mask from Skyrim. The original enchantment reads: +50 Magicka, -20% Restoration and Destruction Magicka cost., dragonborn who can cast spells, Damage, Buff, Headwear