You found a Keystone! Keystones are used to open Spirit Gates. Remember that each Spirit Gate will require a different number of Keystones. - Ori and the Blind Forest
Keystones are collectible items that are essential to progress through Nibel and open Spirit Gates. When Ori finds a spirit gate, they will need to collect two or four keystones (depending on the amount of keystones required) to open it.
Keystones are placed in locations that help challenge the player and apply skills learned to collect them. The number of keystones required in each area is given below: