The Kanohi Elda was the Kanohi Mask of Detection.
The Kanohi Elda was the Mask of Detection. It allowed its user to find the Mask of Life wherever it might be. Hahli was possibly the most important of the Toa Inika because her mask would lead them to the mask they sought.
It allowed Toa Inika Hahli to detect the presence of the Kanohi Ignika and see Matoro's spirit when it was free of his body.
The Kanohi Elda, the Mask of Detection, could find the Mask of Life wherever it might be hidden.