Kaveh had once lived in Sumeru, but due to how others treated him, and how he was broke, he went and joined the Fatui.

He one day came back to Sumeru, he was the 12th harbinger, since he had become quite good at his new lifestyle. He was looking for his target...and that target was you. "So... you are the one who betrayed the Fatui? You worked as their spy...yes?"