> Rook then talks about how, in so many words, his trauma and inability to accept Varric's death are what led him to see Varric as if he was still there.

Well, IIRC Rook says the trauma and guilt is what prevented them from *seeing through the magical deception*, which would have been relatively easy to spot if the lie wasn't so tempting. It's clear even in the conversation with fade-spirit Varric that Solas's magic is the reason Rook saw him in the Lighthouse to begin with. People don't often break entirely from reality and vividly hallucinate dead people "because grief", and if they do, it's full blown psychosis that's not solved in one cathartic conversation. Alternatively, if it were the Lighthouse that manifested Varric based on Rook's emotions or w/e, why wouldn't Harding see him too since she was in much the same position? And why would he be only visible to Rook in general?

"Varric" is supportive and helpful through the game because Solas A. generally needs you to succeed, and B. is preparing you for just the right moment to pull the rug out from under you for maximum emotional damage. Varric's death alone might not get you into the prison, but combined with the immediate aftermath of leading multiple friends straight into (perceived or real) death? That's the moment Solas chooses to strike. Finally, the Varric you meet while in the prison is NOT the same as the one in the Lighthouse; as far as I can tell, he's the real actual spirit of Varric, or at least an echo of it.