The Barghest Contract

Walkthrough
The quest shouldn't be a problem at all. You will find barghests just everywhere in the outskirts at night. Look for rabid dogs or do the Vesna Hood quest - both are guaranteed locations for barghests. After you've collected ten skulls, see Abigail for a nice XP boost and some coin.

Barghest Skulls
Abigail, the local herbalist, will pay cash for barghest skulls. I should see her as soon as I collect the number she needs.

Loot
I have enough barghest skulls to collect my reward. I should see Abigail.

Payment
Abigail paid me for the barghest skulls. Job done.