Did Cole know? ((spoilers)))

Cole may have known. Some of their discussions are speculated to elude to things that could have happened during his time as Fen'Harel, and Cole does seem cognizant of Fen'Harel's nature during Trespasser.

Wait, how did Solas mind-wipe Cole at the end of the main game? I don't remember that.

I was under the impression that he blocked Cole out of his thoughts. It's in the banter, but right now, I really don't want to go searching for it.

EDIT: Whoops, lynroy took care of it!

Yes, I'm sure it was Solas doing that to Cole. Solas is a Somniari and we really don't know the true extent of what they can do. However, they do seem to have abilities that are similar to those of spirits and also replicate what blood mages are said to be able to do (which I've never been sure but I think require the co-operation of a spirit/demon to achieve). According to Mihris in Masked Empire, the Dalish believe the Somniari could see the whole world from the Fade, could tell their allies where their enemies were and in what numbers and where the Veil was thin send spirits to aid their followers (of course in ancient times there was no Veil so they simply sent spirits to help). Then Felassan says while mocking her "They could kill their enemies as they slept." That is something that was formerly claimed for blood mages and so I think actually they were capable of this but Felassan is trying to throw the listeners off knowing what they could really do by ridiculing it.

So just as Solas can take us to the Fade and control our experience of it while there, I think it would be fully within his power to wipe memories, just as Cole does. In fact Imshael claimed to be able to do the same, have spirits whisper in dreams to get people to do things and then make them forget they ever did it.

What is odder is Cole's reaction towards the end of Trespasser. When we are chasing the Qunari through the network after Solas, Cole says "he is not that sort of wolf" when it is suggested that Solas is dangerous. May be Solas was shielding his thoughts from Cole so he wasn't aware of his intentions but then in the epilogue screen, a spirit Cole says he will be ready to return from the Fade as he will be needed. So it would seem he must at least be partially aware of Solas' plans. Why Cole would be willing to defend the actions of Solas when his avowed aim is to destroy the world is something of a puzzle. Solas might seem to feel bad about what he is intending but when all is said and done, a lot of people are going to suffer by it, even if they don't actually die, so aren't they the ones deserving of compassion?