This is my own Toa Vahi, the Toa of Time.
In my (non-canonical and in-the-far-future) storyline, the mask came to life after being lost in a vast sea of energised protodermis, and over time it learned of its past from the Great Spirit himself. Now aware of the destruction that had been caused in the past by attempts to gain pocession of it, in much the same way as the Mask of Life did, The Mask of Time created itself it's own body out of the protodermis. Blinded by disgust of the selfish greed for power that had been the cause of so much death, it swore that conflict would never again arise as a result of its existence by destroying all whom had the capability of starting a new one; namely, every sentient being in the universe. Its one and only weakness is exposure to the protodermis from whence it came.