Several millennia prior to the Battle of the Mask Makers, Makuta and Ekimu agreed on a set of paramount rules that would govern their mask-making in order to preserve the natural order of the island. One of these rules was that any mask containing elemental powers must be limited to a single element, as a provision to prevent any single mask from growing too powerful or unstable.
For centuries, Makuta complied without dissent to these rules; however, by the era of the mask maker's battle, he had slowly turned to bitterness as most villagers held Ekimu's metalworking in a higher regard his own. After several abominable attempts at forging masks with only two powers each, he decided to create a mask holding the powers of the six elements connected to the regions of Okoto. This creation, terrifyingly unstable since its genesis, was the Mask of Ultimate Power.
Fortunately, Ekimu had inferred that a prophecy foretelling doom on the island was to be connected to his brother, and he rushed to the Capital City, where a demonstration of the mask's powers were being held. Rushing to stop Makuta from harnessing the power of the mask, he knocked it from his brother's face with his Hammer of Power. The catacylsmic explosion caused by the destruction of the mask transported the whole of the city to the Shadow Realm, where it would remain until the Second Battle for the Ancient City. The mask, shattered into several fragments, was cast over the six regions of the island.
By the era of the Uniters, Makuta was anxious to escape from the Capital City, which was still trapped in the Shadow Realm. As the Destroyer, Umarak, now a brutish slave of Makuta, was tasked by his master with recovering the disparate shards of the mask, in the hopes that the completed mask could enable Makuta to escape his prison. Despite the efforts of the Toa, who rushed to the site of the Battle of the Mask Makers in an attempt to halt Umarak's progress, the Destroyer succeeded in assembling all of the pieces of the mask. During the ensuing duel between him and the Toa, the shards of the mask were lost. Their exact location remains unknown.