You are asked to find "the largest and meanest kwellen" and return to Bragha when you have "a large piece of Kwellen Hide".

Not sure which kwellen it means for you to find... I've been in groups that have killed SoG and Daknor many many times. They must be close to being the biggest and meanest.
I've also killed a large number of the kwellens roaming the Staging Grounds/Spirit Swamp and also the ED.

So far the only hides I have found on kwellens are the event hides (scorched/charred portions and scraps etc) from Daknor and the normal kwellen hides, neither of which advance the quest.

Anyone got any hints?