Elda

The Kanohi Elda was the mask of detection. It was worn by Toa Hahli. It gave her a headache in relativity to a goal. During the quest for Ignika, the bigger the headache, the closer the Toa Inika were to the Mask of Life. The mask was able to detect Matoro when he was in spirit form. Other ways of "detection" have not been seen.