Of Arthurian legend, Mordred is the son and nephew of King Arthur. Son and nephew because King Arthur made the mistake of having sex with his own sister; therefore the general public thought Mordred was bad blood. Then Merlin, a prophet/wizard/whatever, predicted King Arthur's own son would someday kill him, so King Arthur sent 40 of his baby sons out to sea to die. Only one survived; Mordred.
Mordred was raised by a fishermother and fisherfather, then taken away by a sorceress named Nyneve to live with Mordred's mother in the Kingdom of Lothian. At age 15, Mordred went to serve as a knight to King Arthur. He was invited to the round table.
At age 27, Mordred died. Merlin's prediction was true; in the Battle of Camlann, King Arthur stabbed Mordred in the stomach, causing it to go all the way through his body. But at the last second, Mordred crushed King Arthur's head with a sword. This left Mordred dead, and King Arthur mortally wounded.
Now, in MY opinion, I think Mordred would NEVER had killed King Arthur if everyone didn't treat him as if he was a cursed child; In the book "I Am Mordred" by Nancy Springer, it explains much of this, but anyway, Mordred was shunned as, when he was little and nobody accepted him. Had not people avoided him, had not people feared him, had not King Arthur sent all his babies to die, they both would have lived and died peacefully.
I advise you to read "I Am Mordred" by Nancy Springer if you want to learn more. It's a great book.
Sir Mordred of Camelot.