This is Kazakh, Okoto's Bringer of Nightmares.
He was once a Master of the Mind, a Toa of Dreams. But upon his untimely death to the evil Makuta, Kazakh was mutated into an ethereal being that only entered the mortal world at night.
He is the "Bogeyman" the Okoto villagers tell tales of about their campfires, and the "Closet Monster" that keeps children in their beds. Every night, he acts as the human's "Sandman" does, spreading nightmares about the island, keeping the people subdued by fear.
Will the Uniters be able to defeat such a threat? Only time - and dreams - will tell.
Idea credits for this MOC go to:
@Ghosty, who I believe created this head idea originally.
And the LEGO Group for creating the Irnakk titan model, which Kazakh is based off of.