This is a Mayan Ceremonial Crystal Skull Mask(It is made of a rare green stone called guatemalita), it was discovered in the Tikal region. It was used by ancient Mayan Shaman when they officiated ceremonies. Once it was placed over their head, the Shaman would be “transformerd” into Kemé - el señor del inframundo” - a Lord of the Infraworld. This would grant them magic, energy, and the power of purity. Looking through it’s eyes would allow the Shaman to see into different worlds.