Ascanen Vanwa (Gil-galad_of_Lindon)
She was born in Eregion in 1250, while Sauron was teaching the elves there how to increase their talents with metal. Her brother was one of the elves learning from Sauron, and he helped forge the Three Rings. After Celebrimbor perceives Sauron’s plan, Ascanen went with her brother to hide Narya with Cirdan in the Grey Havens. On the way, their group was attacked. Several elves, including Ascanen, were taken to Barad-dur. Ascanen remembers none of this. What she does remember follows.
Sauron used them in an experiment to create servants superior to the orcs and goblins, but it failed. Many died because the torture was too much. Ascanen was the closest to becoming what Sauron wanted, but her mind had become fragmented in the process. Sauron had her torture other captives, and trained her in various fighting techniques.
Finally, her brother came to rescue her. But she didn’t remember him, and fought him. He failed that time, but returned shortly. He was more prepared the second time, and used a potion to put her to sleep. He tied her up, and took her out. He spent months trying to make her remember, but she would only curse him in the Black tongue. He took Ascanen to Rivendell, where he hoped someone could heal her. Elrond and the other healers did their best; afterwards Ascanen no longer cursed at her brother, and she did not have such a strong desire to return to Mordor. Elrond suggested that Ascanen be taken to Lothlorien, a place neither she nor her brother knew of, to rest.
In Lothlorien Ascanen did become more normal, and became more like her former self, like in Eregion. The disconnection of the Wood from the rest of Middle-earth helps her to disconnect from her darker past.