It is a new piece of headgear armor.
An eerie mask passed down from ancient times. Wearing it makes it harder for certain enemies to spot you. If sold, this rare find can't be replaced.
- Armor Level 1
- Low level enemies ignore you
"The ancient mask lies at the ruins where soldiers gathered. From there, the waters of Lake Kolomo are visible."
Majora's Mask Location
The chest is located in The Kolomo Garrison Ruins. The chest itself is buried in the ground right outside the main building in the corner on the south end.