Aeons ago, in time immemorial, the Great Spirit of Mata Nui faced a terrible betrayal at the hands of that which he once called brother. A powerful being whose name was all but lost to time, once as pure and benevolent as the great Mata Nui himself, was twisted by the darkness of hatred and envy. He took up arms against those he had been sworn to protect, forcing Mata Nui into a deep sleep and bringing about one thousand years of darkness. But with the help of countless brave souls, balance would be restored. Mata Nui's betrayer would be all but destroyed, and the fragmented remains of his essence would be locked away, never to harm another soul ever again.
Or so it was thought.
In the millions of millenia since, the many sacrifices and great deeds which were necessary to ensure the continued survival and freedom of the Matoran Universe were forgotten, and the changes made to prevent such events from ever recurring have been undone over the ages.
The Order of Mata Nui, once the Great Spirit's most trusted of servants and gleaming icons of justice, have degraded into a bloated, rotting carcass of their former self. The Matoran Universe reeks of corruption and self-interest. Mata Nui is falling gravely ill. And deep below, an ancient evil feeds upon his sickness.
Fueled by the sins of an entire universe, the betrayer stirs. Life flickers through passages long untravelled, thoughts trickle down metaphysical synapses long idle. A disembodied voice speaks in hushed tones of nightmares and unspeakable depravity. Deep below, he lives again.
His essence grows and throbs like a cancer, screaming silent profanity at a universe that cannot hear him. He thirsts; he hungers. He longs for vengeance.
His rage builds, and from his hatred he is remade with a earth-shattering howl, deafening yet silent all the same. Darkness consumes many a realm, and Mata Nui can stand the agony no longer. The Great Spirit falls asleep once more.
The betrayer's screams ring clear in the minds of all who inhabit this universe, sending chills down their spines, for the voice echoes with an unknowable yet familiar evil. "Hear me," it implores.
"Hear me, for I am reborn. Hear me, for I am Teridax. Hear me, for I am Makuta, the Master of Shadows. Hear me, for soon I shall rule you all."