He was injured very badly by the organization that raised him in return for leaving them, for not taking their contracts.

[ This is said a bit more shortly than everything else has been to this point, but then Merrill sighs. ]

Have you heard of Kirkwall, while you've been here? Of Knight-Commander Meredith, and how she was corrupted by red lyrium and tried to kill every mage in the city?

I was there. He helped my friends and I stop her.