Heidrek or Heiðrekr is one of the main characters in the cycle about the magic sword Tyrfing. He appears in the Hervarar saga, and probably also in Widsith, together with his sons Angantyr (Incgentheow) and Hlöð (Hlith), and Hlöð's mother Sifka (Sifeca). The etymology is heiðr, meaning "honour", and rekr, meaning "ruler, king".
Heidrek was the son of king Höfund and his wife Hervor, a shieldmaiden. Like his mother in her youth, he was ill-natured and violent. To amend this, he was raised by the wise Geatish king Gizur, but this did not improve his disposition. One day, when his parents were having a banquet, Heidrek arrived uninvited and late at night, he started a quarrel which ended in manslaughter. His father, King Höfund, banished Heidrek from his kingdom, although Hervor did her utmost to soften Höfund's feelings against his son.
His father's advice
However, before Heidrek left, his father gave him some words of advice:
"Never help a man who has betrayed his master.
Never give peace to a man who has murdered his friend.
Don't allow your wife to visit her family frequently, even though she insists on doing so.
Never tell your loved one about your secret thoughts.
If you're in a hurry, never ride your best horse.
Never punish the son of a better man.
Never break a promise about peace.
Never have many thralls in your company."
Heidrek immediately decided never to follow his father's advice.
Hervor secretly gave her son the sword Tyrfing as she bade him farewell, and his brother Angantyr kept him company for a while. When they had walked for some time, Heidrek wanted to have a look at the sword. Since he had unsheathed it, the curse the dwarves had put on the sword made him kill his brother.