The reward for this sidequest is self-confidence.

At 9S's question, Cole nods. "I could forget, but not show others." There's a pause, before he continues. "I found Lavellan."

Which still tears him up a bit inside. Someone so strong and so caring shouldn't be forced and changed to act like this. The Void had hurt her and made her so unlike herself, and Cole doesn't know how to get her back.