Damien (Mousa Kraish) was one of the four Intersect candidates who matched Chuck's psychological profile. He is first seen in: "Chuck Versus the Muuurder".
A Greek American CIA agent, Damien is a former Navy SEAL who won an award for marksmanship. However, his "swarthy, bearded" led the agency to embed him in one terror cell after another for ten years. Despite excelling at both physical and "cultural" testing, Damien is not chosen for the Intersect.
When Chuck's first choice, Brody, is found murdered, Damien believes that he is being suspected because of his appearance and angrily leaves. As he opens the door to exit Castle, an explosive is triggered, injuring him and ruling him out as a murder suspect. However, Chuck later realizes that Damien really was the murderer, having strategically detonated the explosive and shielded himself with a door.
Damien threatens to detonate a boombox full of explosives if they do not get him to a doctor, but Bentley shoots him and retrieves the boombox. After Damien is interrogated, it is revealed that he was paid $10 million by Vivian Volkoff to kill Chuck.