Percival

"He wasn't always like that. There had been a prophecy surrounding him and due to that, in the envy of too many sorcerers and sorceresses, he was cursed. Every day, as long as the sun shines, he is enveloped in goodness. And when the moon reigns... well, you've seen his evil side. Due to that, he was known by many knights to be "The Knight of Good and Evil". But despite that conflicted nature of his, he had vowed to never hurt the women and the children. No matter what happens, he may kill innocent men when he was controlled by the night... but he'll not condemn women and children to be involved in a world that is meant to be battled by men."

- Sir Tristan to Eira Prowell

Sir Percival is the son of King Pellinore of the Isles, the younger brother of Sir Aglovale, older brother of Sir Lamorak, adoptive older brother of Sir Tor, all of them who've been members of the Knights of the Round for quite some time before he finally overcome the curse surrounding him and vowed to forever in service of King Arthur Pendragon of Camelot, Logres and the Britons. Due to his unrivaled innocence and kindness among the sons of King Pellinore, it had been prophesied that he'll be one of those who'll find the Holy Grail, a collision to that of the prophecy surrounding Sir Galahad. Due to the unrivaled jealousy of Morgan le Fay, she and other mages condemned him to be cursed: that everyday, he'll be a good knight by day and be the embodiment of evil by night. With his attitude out of control, King Pellinore allowed him to leave and venture on his own. Despite the curse, Percival vowed to never hurt women and children. Later, it was revealed that he was originally cursed for allowing women and children be condemned during his first fight as a knight when he can do something about it.

He breaks the curse later on himself with the help of Eira Prowell who've ventured through his soul that he can control that evil side of his if he wanted to. It appears that the only way for the curse to be lifted is for a woman to understand the true depth of his soul, and Eira managed to reach that of his. He then become one of the Knights of the Round afterwards, and along with Galahad and a selected few, they are sent by Arthur to find the Holy Grail. He had been spared from death compared to the countless other members of the Knights of the Round that perished during the Battle of Camlann, as well as their king. Due to that, he and the surviving ones had ventured to keep the promise of ensuring that the legend of their king will live on throughout time before they scattered away and fulfill Arthur's wish to have his nephew, Constantin II, become the next king.

Background
Percival was the second son of King Pellinore of the Isles. As a child, he was prophesied to be one of the few who will find the Holy Grail. He was cursed as a child, due to Morgan le Fay's jealousy of his purity and innocence, to have a rather bipolar personality that was affected by the time of the day. During the morning, he was on his good-natured personality; while during the night, he was controlled by darkness. Despite it, he had vowed to never hurt women and children at all cost. He had left his father's kingdom in search of work that would be enough for him to survive, earning him a name to be the knight whose loyalties lie to the highest bidder.

Sword of Light
Percival first appeared to be one of the many knights that were longing on one bar and inn close to Camelot, and one of the intrigued ones about the happenings in Camelot regarding the succession to the throne and those brave knights who've tried to pull the sword off the stone. He was first said to be friendly and charming by Eira when he helped her and Arthur escaped the people who were trying to steal from them. Later that night, Percival had attacked Eira to be assassinated, mentioned to be ordered for him to do with an equivalent large amount of money in return. However, he was stopped by Sir Tristan and learned that Eira was a woman, saying then that he had vowed to never hurt women and children.

Trivia

 * According to Flaire, Sir Percival's inspirational song in the series is "I'm a Wanted Man" by Royal Deluxe.