Mineru is a character in Tears of the Kingdom.
Tears of the Kingdom
"Elder sister of Rauru. She helped her brother, the source of Link's right arm, fight the Demon King in her role as the Sage of Spirit long ago. When she was struck down in battle, she used her powers to preserve her spirit in the Purah Pad. She feels responsible for a Zonai secret stone giving rise to the Demon King and swore to Zelda she would do everything in her power to defeat him in the present day."
Mineru is one of two remaining Zonai in Hyrule, along with her brother Rauru. She is known for being an expert in the way of life and history of the Zonai. She possess a Secret Stone which allows her to separate her spirit from her body.
When Zelda was transported to the early days of Hyrule, she and Rauru consulted Mineru for a way to return Zelda to her own time. Mineru believed that it was the power of Zelda's stone that allowed her to travel through time, having amplified Zelda's own power over time. She did not think that the stone would allow Zelda to return to her time. Such a thing would require Zelda herself to know how to control her power and use it properly.
Mineru does mention an alternative action called draconification, which involves swallowing a secret stone and turning that person into an immortal dragon. This, however, is a forbidden act, as it will cause that person to lose themselves and everything that makes them who they are.
After Ganondorf's rise to power, Mineru uses her power to fight as the Sage of Spirit during the Imprisoning War. She, like the other Sages, is unable to effectively fight against Ganondorf, and only Rauru's sacrifice is able to defeat him. Gravely injured during the fight, it is inevitable that she will die soon afterwards. She uses her remaining time to assist Zelda in repairing the Master Sword. Mineru tells Zelda that the Sword could take centuries to grow strong enough to defeat the Demon King, and protests when Zelda plans on using draconification to reach that goal. She relents after seeing Zelda's dedication, and promises that she will aid Link when his time arrives. Mineru's spirit enters the Purah Pad, where it remained until present day.
After finding four of the Sages and defeating Phantom Ganon at Hyrule Castle, Link is without a path forward. Purah realizes that there is another Sage in the tale of the Imprisoning War who is still unaccounted for. She asks Link to pursue this Sage to see if they can offer any assistance. With assistance from Tauro and the Zonai Survey Team, Link finds ruins that also speak of a fifth Sage. These lead to a mask that is hidden on Dragonhead Island. After finding the mask, Link hears a voice that advises him to take the mask and follow its light, beginning the Guidance from Ages Past Main Quest.
Following the mask's light leads Link to Tobio's Hollow Chasm, and an elevator that leads into the Depths and the Construct Factory. Upon putting the mask on a partial Construct at the Factory, Mineru introduces herself as the Sage of Spirit. As she no longer has a body, she asks Link to find the other missing parts to the construct by exploring the four storehouses in the area. Once Link has assembled the Construct, they make their way across the dangerous Depths, and to the Spirit Temple found nearby.
Once Link defeats a Seized Construct, the secret stone found in the Temple will allow Mineru's spirit to leave the Purah Pad and enter the construct. She explains that her intent was to awaken when he found the Purah Pad and guide him to the construct to assist on his journey. This was not possible, due to the gloom's influence over her construct. She admires Link's abilities and gives him her power, allowing him to use her spirit and construct whenever necessary.
Mineru tells Link the origins of Zonai, the early days of Hyrule, the Imprisoning War, and how Zelda came to possess the Master Sword. She tells Link that the Master Sword is the strongest weapon to defeat the Demon King, and does not doubt that it is located somewhere in Hyrule. Mineru advises Link to seek the Deku Tree, as Zelda intended for Link to meet him when he needed the Sword. She tells Link that she will remain in the Spirit Temple to work on the construct body in preparation for the final battle, and gives Link the Vow of Mineru before he departs. This completes the Guidance from Ages Past main quest.
In a post-credits scene after completing all Main Quests, Mineru, Link, Purah, and all living Sages appear behind the Temple of Time. Mineru tells Zelda that it was likely Rauru and Sonia who gave Link the power necessary to turn the Light Dragon into Zelda once again. Believing that they have overcome the burden the Zonai left to Hyrule, and having completed her promise to Zelda, Mineru says it is her time to move into the afterlife. Before leaving, she says she will tell Rauru and Sonia just how much Zelda cares, and thanks everyone for all they've done.