Ultimately, Arton began plotting against Eddin. It is revealed he had a hand in the joint assassination of Grayson Mercer, conspiring with Grayson's brother, Ser Roman Mercer, and the Blackwatch; at the time, Arton was only partially aware of House Bergen's role in the assassination, and had no knowledge of their alliance with the Greyjoys. At Trevyr Blackgard's funeral, Arton arranged for Eddin's assassination at a peace summit set up by Grand Maester Pycelle, who had become Cersei Lannister's spy. The summit was to be held at a remote castle near Casterly Rock, where Eddin would supposedly be safe. In return, Arton would inherit the city of Blackgard. However, Eddin had anticipated the plot by way of a warning from his father, who intimated that the person who approached him about the peace summit would be the traitor. Asten Wylde initially thought the traitor would be Theos Tymber, but Eddin was not surprised, since Arton was always the smarter one.
As Arton and Asten were preparing to attend the summit, Ser Markas Warth told him that Eddin was coming in a separate carriage. Arton was visibly upset, saying that it threw off his "arrangements." Asten says he can't come along either, and several of Arton's men surround him. Realizing that Eddin has found out about his treachery, Arton asked Asten to tell Eddin that it was "only business" and he always liked him. Arton then asked Asten if he could get him off the hook for "the old times' sake". Asten rejected his appeal. How exactly Arton was killed is unknown.