Seth

Seth is an agent, who is under the leadership of Ling. He was ordered to enter the King Of Fighters tournaments to investigate Ron's activities and capture him. Seth later finds out, that Ling was actually Zero, who posed as Ling.

Seth continued to search for Ron. He eventually got invited to attend a meeting together with his fellow agents, which was held by Heidern.

Seth also gave Fate some information about Duke. Because of this information Fate stood up to Duke and eventually got killed. Because of this Fate's adoptive sons, Alba and Soiree, think that Seth is partially responsible for his death. That's why they target him during the King Of Fighters tournaments.