The Krana Bo was the sentinel Krana. It gave its user the ability to see in the dark. It was worn by the Bohrok and was one of the eight types of Krana. The Krana controlled the Bohrok, and the Bohrok could not function properly without them. All Krana were made by the Bahrag sisters by adding Energized Protodermis to an unknown form of energy. The Toa Mata collected one of each type of Krana from each species of Bohrok, and these unlocked the chambers containing their Exo-Toa armour.