- He is the Defender of young knights his right arm is longer and was accidentally killed by Lancelot which ended the round-table
- Gaheris is nephew to King Arthur and Squire to his elder brother Gawain, whose fiery temper he helps moderate, before being knighted himself.
- He helps kill King Pellinore out of revenge for his father’s murder and Sir Lamorak, Pellinore’s son and his mother’s lover.
- He beheaded his own mother Morgause after catching her with the youthful and handsome Lamorak, who escapes.
- Hunted down by all of the brothers except Gareth. Lamorak is greater than any knight except Lancelot and Tristram, so the Orkney brothers’ act of revenge is deemed cowardly and a blot on their honor.
- Arthur and the brothers discover that Gaheris is Morgause’s slayer, and he is banished from court.Despite being exiled, Gaheris appears when he and his brother Gareth are accidentally killed by Lancelot during the rescue of Guinevere.
- Gaheris and Gareth do not participate with Agravaine and Mordred’s plot to entrap Lancelot and Guinevere, and Arthur asks the brothers to help guard the Queen’s execution.
- Gaheris and Gareth reluctantly agree, though Gawain refuses.
- They decline to wear armor and Lancelot is unable to know who is his enemy or friend in his blind rage to save the woman whom he loves.
- He accidentally kills down the unarmored princes.
- When he is later told what he did Lancelot is emotionally destroyed, because he loved Gareth like a son. Gawain’s fury at this outrage is terrible and the fighting breaks the Round Table.