Nimue (character)

Nimue is a minor character on the ABC show Once Upon a Time. She debuts in the eight episode of the fifth season, "Nimue". She has no Storybrooke counterpart.

Before the First Curse
Nimue lived in a small village located in or around Camelot, before it was burnt to the ground. Being the sole survivor, she fled to another village that was under the protection of Merlin's magic.

She and Merlin eventually fall in love, and wants to make a life with him, when Merlin reveals that he obtained his magic and immortality from from the Holy Grail, and that he can't be with her because she can die and he can't, Nimue convinces Merlin to take her to the Grail so she can drink from it. They do not realize that the masked man who destroyed her village listens to their conversation. When Merlin takes her to the spot where he found the Grail, they pass by the little remains of her former village. They realize they were followed by the masked. As Merlin tries to fight him off with Excalibur, Nimue drinks from the Holy Grail. Eventually Nimue is stabbed by the man and dies in Merlin's arms. As Merlin heads off, Nimue gets up. Astonished, Merlin asks how she survived, she reveals that she drank from the Grail, giving her magical abilities.

She pulls the man's heart from his chest. Merlin tries to persuade her to put it back, as killing the man would turn her dark. Niue feels revenge is the best way to deal with the man, and she crushes his heart. She immediately turns into a dark being, called the Dark One, with her skin turning a gold-ish green, and her eyes changing color. She grabs the mask of the dead man, putting it on her face. Wanting to have all the power, she turn the Grail into Excalibur. The sword is eventually broken, and Nimue takes the smaller piece of the blade and turns it into the Dark One's Dagger.

At some later point, Merlin manages to steal the Dagger from her, and places enchantments on it that will cause Nimue to be controlled by whoever is in possession of the dagger. It is unknown if Merlin keeps the dagger to control Nimue, or if she manages to get it back.

After the Second Curse
After Emma Swan becomes the new Dark One, Nimue and all the previous Dark Ones, including Rumplestiltskin, exist as voices in Emma's head, instructing her one what to do. Nimue convinces Emma to rejoin the dagger to the rest of Excalibur, which she succeeds in doing.

Trivia

 * Nimue is the first person to ever become the Dark One
 * She also created the Dark One's Dagger.
 * Despite being immortal from drinking from the Grail, she can be (and most likely was) killed by the dagger
 * She is the only other known female Dark One, besides Emma Swan.