Location: Valthume
Class: Heavy Armor
Enchantments:
Resist Disease: 100%
Resist Poison: 100%

Location: Shearpoint
Class: Light Armor
Enchantments:
Fortify Lockpicking: 20%
Fortify Archery: 20%
Fortify Alchemy: 20%

Location: Labyrinthian
Class: Light Armor
Enchantments:
Regenerate Magicka: +100%

Location: Skuldafn
Class: Heavy Armor
Enchantments:
Fortify Magicka: 50 points
Destruction spells cost: -20%
Restoration spells cost: -20%

Location: Ragnvald
Class: Heavy Armor
Enchantments:
Resist Fire: 30%
Resist Frost: 30%
Resist Shock: 30%

Location: Forelhost
Class: Heavy Armor
Enchantments:
Fortify Stamina: 70 points

Location: High Gate Ruins
Class: Heavy Armor
Enchantments:
Conjuration spells cost: -20%
Illusion spells cost: -20%
Alteration spells cost: -20%

Location: Volskygge
Class: Light Armor
Enchantments:
Fortify Barter: 20%
Fortify Carry Weight: 20 points
Waterbreathing

Location: Bromjunaar Sanctuary in Labyrinthian after collecting all the previous masks.
Class: Heavy Armor
Enchantments:
Healing
When the wearer is struck while below 15% health, there is a 15% chance that the mask will heal the wearer and any nearby allies with the Grand Healing spell, and grant a Flame Cloak for 10 seconds.
Spectral ally
Whenever the wearer is struck while below 15% health, there is a 3% chance that the mask will not only restore the user's health, but also summon a Spectral Dragon Priest ally. The said character may use Ice Spike and Reanimate Corpse. Should corpses be absent, the Dragon Priest will instead summon a Storm Atronach.

All information is from The Elder Scrolls Fandom Wiki.

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