The Mask Makers resided on Okoto during its Golden Age, forging many Masks for its inhabitants and protecting the island alongside the Protectors. They worked in the Forge, in the City of the Mask Makers, whilst travelling in airships around Okoto.
They both understood the dangers of tampering with the island's Elements, so they formed a sacred agreement declaring they would never forge a mask with more than one element.
As time passed, Ekimu grew more respected by the islanders, thus causing Makuta to become envious of his brother. When the Skull Raiders attempted to invade, the two brothers worked with the Protectors to drive them into the mountains of the Region of Stone. Later though, unknown to Ekimu and the Protectors, Makuta approached the leader of the Raiders, Kulta. He offered him an alliance, stating that he would call upon Kulta when he had need of an army, and that he would allow Kulta to avenge his defeat by allowing him to attack Okoto. The two agreed.
Eventually, discarding the agreement between himself and Ekimu, Makuta tried to create the most powerful mask of all time, the Mask of Ultimate Power, which combined the islands six elements. However when he donned the mask, its power consumed him.
Ekimu attempted to stop and save his brother, using his Hammer of Power to remove the mask from Makuta's face. However, this caused a shockwave to spread across the island, altering its very formation. It knocked Ekimu into an endless sleep, also dragging Makuta and the Capital City into the Shadow Realm, only leaving behind the Black Crater behind as proof of its existence.
Centuries later, Makuta's influence returned to the island and he attempted to break free of the Shadow Realm. However, he was ultimately defeated when the Toa drove him back through the portal Umarak had created with the shards of the Mask of Ultimate Power