Source: Candlekeep Mysteries

Wondrous item, very rare (requires attunement)

While you wear this helm, you gain a +1 bonus to AC and remain aware of your surroundings even while you're asleep, and you have advantage on Wisdom (Perception) checks that rely on sight.

As a bonus action, you can cast the See Invisibility spell from the helm. Once this property of the helm is used, it can't be used again until the next dawn.