Having finally managed to defeat Ganon inside the Pyramid of Power and recovering the Triforce, Link used the legendary artifact to restore all of the damage and horror that the Dread King and his minions caused.
After Hyrule and the Sacred Realm were returned back to their former glory, the Triforce itself spoke to Link. The essences of each of the goddesses that formed the Triforce were exhausted after ages of being misused and shambled about by the forces of evil and the greed, and were tired of being unable to really do anything to actually protect itself.
The Triforce, feeling as if Link, who held within him the spirit of the hero, possesed a suitable balance of Power, Wisdom, and Courage to suit its desires to rest and be better protected. Before the young hero could say or do anything, the ancient artifact quickly proceeded to merge with him, changing him to his very core, where they became one.
In the process, due to being combined with the raw essence of the three Golden Goddesses that crafted the Triforce, Link found his body transformed into that of a female. ‘She’ had become an embodiment of the Triforce itself.
As an embodiment of the Triforce itself, Link now holds vasts amounts of power, though at the same time is a bit of a victim of her own whims and the stimuli around her.
As the Triforce itself, she is capable of granting wishes and power to those who seek her out. Though thanks to the merging and actually possessing a body and more advance sapience and understanding, is capable of more control over who and what gets wished for. She is also capable of twisting the results of wishes if she is capable of finding a loophole.
Though she is now unable to freely move about anywhere she desires now due to the potential dangers of having the Triforce carelessly adventure about, she is capable of creating a sort of spirit body of herself that actually is able to go out and explore and fight against evil.
The spirit body, on its own, lacks the majority of the power that the ‘main’ body possesses, but is comparable to the capability that Link had before the merger. As a spirit, she is also capable of possessing others.
If split apart into the three aspects of the Triforce, Link ends up as three different tiny sprites. Each of them an embodiment of the piece they represent. If someone manages to take control of said piece, then they will also find themselves in possession of a Link Sprite that is constantly flittering about them.
Side note, Wisdom is the cutest!