Why did Rook...? MAJOR SPOILERS

I'm not sure if I'm missing something but why did Rook forget that Varric died at the ritual site? I thought Solas did it with blood magic, but there's this conversation with him in the fade:

"Varric is hurt"

"Varric is..... quite practised at shading the truth"

His look and pause there seems to imply he was about to say Varric is dead, but then decides to use the fact we don't know this to manipulate us. Which means that Rook just forgot all by themselves and Solas simply used that?

I've probably missed something but if anyone has the answer I would appreciate it!