In 1272, Arnvald was serving at the keep of Kaer Trolde. After the funeral of King Bran, he was sent a letter by Birna that instructed him to spike the mead at the feast with a mushroom known as mardroeme, which changed those who consumed it into vildkaarls. The plan was successful and a massacre occurred in the great feast hall. As the witcher Geralt of Rivia and Cerys an Craite went to investigate, Arnvald attempted to burn them alive in a locked room.
After being revealed as the pyromaniac and enemy of the an Craites, Arnvald fled on horseback from the keep, pursued by Geralt and Cerys.
If Geralt catches him: confronting Arnvald proved no problem, he admitted freely to his crimes and presented a letter of instruction from Birna Bran, instructing him to spike the mead at the feast with mardroeme, though it lacked a signature.
If Arnvald escapes: fleeing to the beach, Arnvald met with Clan Tuirseach warriors, thinking he would be taking a boat from the harbor. As instructed by Birna, the warriors attacked Arnvald to tie up any loose ends.
- If Geralt saves him: arriving in the nick of time, Geralt killed the warriors who had betrayed Arnvald and got information from him.
- If Arnvald was killed: Cerys and Geralt arrived too late. The warriors had left Arnvald's body on the shore, and after a quick look in his boot, Geralt found a small key, their next clue.
After catching him, Arnvald accompanied the witcher back to Kaer Trolde where he admitted to his crimes in front of the council and helped convict Birna.
- After Guthlaf, trusted seneschal to the An Craite jarls, passed away a portion of his duties were taken over by the jarl's cupbearer, Arnvald. This elderly Skelliger did not possess the far-reaching authority of his predecessor, but still had managed to make himself irriplaceable in his few years in the position. His purview included not only stocking the larders and cellars of Kaer Trolde but also seeing to the needs of the keep's inhabitants, as well as the guests that visited it during feasts and other important ceremonies.
- If Geralt catches Arnvald:
- That is why is betrayal could not have come as a greater surprise. When caught, Arnvald confessed to his role in the murderous conspiracy, revealing his patron as well as his long-seething hatred for Clan an Craite.
- If Geralt fails to catch Arnvald:
- That is why his betrayal could not have come as a greater surprise. His motivations, however, remained a secret that he took to his grave, for he died while trying to escape, killed on his patron's orders.