Mata Nui And Tren Krom
Tren Krom's island is the southernmost island in the chain leading down from the left side of Mata Nui - his right, our left. Since it's the southernmost island, I'm thinking that this would correspond into being inside/near the hand.
Tren Krom was in Mata Nui's right hand.
He was his right-hand gelatin monster freak thing.