Farkas wishes to be cured of his lycanthropy as well, and so we must once again travel to the Tomb of Ysgramor to perform the same ceremony that we did on Kodlak. Agree to help him out with this and he will become your companion for this quest.
You need a Glenmoril With Head to do this quest. Hopefully you killed ALL of the witches when doing the main quest for Kodlak which gives you enough heads for everyone–including yourself should you ever want to remove the Werewolf powers!
This quest is JUST as easy as when you did it with Kodlak. Actually, I take that back, cause it’s 1000x easier: you don’t have to go through the entire ruins this time! Just head to the Tomb of Ysgramor and take the EAST path down to the fire.
Put a witch head on the fire and out pops Farkas’s wolf spirit. Simply kill it to rid Farkas of his lycanthropy. This will end this quest, and you will get 300 Gold out of the deal! Very nice.