Blood Crystal

A blood crystal is a crystal which allows the wearer of the crystal to take on the physical appearance of anyone who's blood the crystal touches.

After the two thugs Dagr and Ebon were put in the stocks after a bar brawl that had just ensued in the tavern due to the barmaid not giving Dagr some money. Later the two thugs visited a sorcerer who gave them blood crystals and Starlorne blades which appear blunt to the eye but in reality the blades themselves are razor sharp. After killing the sorcerer they came across two kinghts who were going to take part in a tournament in Camelot and killed them. They then took on their physical appearances with the crystals. When they arrived in Camelot when they faced Arthur they almost defeated him but didn't due to the intervention of Gwaine. After the fight Gaius removed the crystals to reveal to Uther the two Knights were really two thugs.