Time to find Kodlak , who's probably in the living quarters, and speak to him. He will tell you that you've had your vengeance and need to STOP killing the Silver Hand. I have to admit, he makes a good point.
He'll then go on about his lycanthroypy and wish to cure it. He will tell you the back history behind the curse and say he's found a cure. But he needs you to go and collect a Glenmoril Witch's head.
And with that our new task is upon us. Note that we can also wipe out all of the Glenmoril Witches; it is optional. Something to keep in mind. If you check out the map, you'll see that the witches live in Glenmoril Coven (well duh!), which is just northwest of Falkreath . So head to the closest place you can and make your way to the Coven.
Once inside the Coven, sneak up to the middle room where you'll find the first witch with a wolf. These witches are a lot like the classic Hagraven enemies and can burn you to a crisp if you let them--ranged sneak attacks work well. Kill them both off and loot the body for the head and that's that!
Note: You can go back to Kodlak now if you wish, or you can kill off the rest of the witches. I'd highly **** recommend killing off the rest of the witches because you can use their heads to cure yourself if you ever wish, but it's your choice. Plus, there's two Skillbooks here we should grab... and it's not even hard!
Well, like I just said in the note, you can go back to Kodlak now if you wish, but the layout of the coven makes it really easy to kill off the rest of the witches. Plus two Skillbooks to be found here.
Instead of holding your hand through this, I'll just tell you that there are four more witches, and this BIG room that you are in now is a HUB room. From here there are four passageways to four other rooms, each with a witch; sometimes a rat, or a spider, or something small to worry about. It's your goal to go to each room and kill the witch in it, which isn't too hard since you fight one at a time.
The Treasures here are in the room with the enchanting table. You can find an Enchanting Skillbook named "A Tragedy in Black" , and in the room with the tent , you can find a Destruction Skillbook named "Horror of Castle Xyr" inside of the tent--it can be hard to see. There's also a chest by the tent that you should definitely loot.
Whether you killed all the witches or not, be sure to grab at least one head and return to Jorrvaskr. As you approach the headquarters, you'll see your brothers outside with several dead Silver Hand.
It seems that in our absence, the Silver Hand decided to attack! Head inside and Vilkas will ask where you've been. Answer however, and then he'll tell you that the Silver Hand attacked, and the only person killed--besides a lot of them--was Kodalk.
They also managed to steal all of the fragments of Wuuthrad that we had! He will then say that he and you are going to go attack their main base, and wipe them out! This ends the current quest, and starts the next Companions quest: " Purity of Revenge ".
Note: Possible glitch: If you return with the witch's head and have another buddy tagging along at the end of 'Blood's Honor', you WILL NOT be able to start the 'Purity of Revenge'. You must walk in solo or else you cannot start the new quest.