The Helm of Yngol is a unique heavy armor helmet found in The Elder Scrolls V: Skyrim. It once belonged to Ysgramor’s son, Yngol, who was killed at sea along with his crew by Sea-Ghosts, as described in Yngol and the Sea-Ghosts.
The helm can be found on Yngol’s skeletal remains within the throne room of Yngol Barrow. The helm is guarded by Yngol’s Shade.
It can be upgraded with a Steel Ingot at a workbench, and also benefits from the Advanced Armors perk, which doubles the improvement.
The Helm of Yngol is considered to be a part of Ancient Nord set, although it has a different appearance to the Ancient Nord Helmet. As this helmet is considered to be part of that set, you can use the Helm of Yngol to replace an Ancient Nord Helmet or Ahzidal’s Helm of Vision, and still gain the Matching Set perk.
This helmet is only one of three helmets in the game with a resistance enchantment (the other two being Otar and Ancient Helmet of the Unburned), one of six with Dragonborn installed. This makes the Helm of Yngol possess one of the rarest enchantments in the game. Oddly enough, the only items with this style of enchanting appear to be of Ancient Nord origin.