A synth who escaped with the Railroad's help, Dejen witnessed their slaughter but managed to evade his pursuers and make his way down to Acadia. He is concerned about security - the refuge is only as safe as it is hidden from the prying eyes of the Institute.[1]
Unlike most of his comrades who accept DiMA's judgment of the Sole Survivor's trustworthiness and treat them kindly, Dejen is highly suspicious of the newcomer and makes no effort to hide it. Successfully completing the quest he offers yields a grudging thanks from Dejen but doesn't change his overall unfriendly behavior afterward.
↑The Sole Survivor: "So, what's your story?" Dejen: "I guess there's no harm in talking about it. I escaped the Institute, found the Railroad. They agreed to help get me out of the Commonwealth. Institute tracked them down, and slaughtered them all. Far as I know, I'm the only one who got away. So, I'm here to make sure it wasn't all for nothing." (Dejen's dialogue)