Sensing that Artakha was in need of a solution to the over-population problem on the Great Refuge without resorting to genocide, Etro Nui suggested they build another planet for half the Matoran to live on, calling it Luminus Magna. She then instructed Arakha and Mata Nui to keep the planet's existence a secret, for Scryptorek's command to kill half of Artakha's people was born of selfish reasons. But despite Artakha's best efforts to maintain the deception that he did as Scryptorek ordered, the Makuta eventually made his way to Luminus Magna. He killed all the Matoran living there, save for Crono, tortured Etro Nui, stripped her of her powers and banished her into the vastness of space. But it has been implied/rumored that despite her banishment and inability to return to and free her planet, Etro Nui had somehow regained some measure of her power and is working to mitigate, or even reverse the damage Scryptorek's actions have done to the timespace continuum. With the death of the evil tyrant who killed her people, Etro Nui is presumably able to finally return to the liberated Luminus Magna to usher in a new age of peace and happiness for both humans and Matoran.
The "Nui" suffix means "great" in Matoran, so her name means "Great Etro".
- One possible explanation to Etro Nui being the same deity across the Fabula Nova Crystalis and possibly even the Final Fantasy series as a whole, including presumably Final Fantasy XV, is that Etro never truly died at the end of Final Fantasy XIII-2; Etro had actually ascended to an even higher, trans-dimensional state of existence between life and death.
- In fact, there is a rumor that Etro Nui had some role in bringing forth the Dawn of the Future, owing to her formerly intended role in Final Fantasy Versus XIII.