The Higher-Ups

 is a quest in.

Synopsis
Harbinger Brythe has asked the Watcher to take care of a problem facing the Rymrgand worshippers of Harbingers' Watch - the cultists that arrived at the Dead Floe before them. These pilgrims have set up camp above the Watch and attack anything they see.

Walkthrough

 * To access the Outcrop on High, you need to complete the first quest in the area, An Honored Guest, and receive Vatnir's icepicks. Then it's a simple matter of heading to the Outcrop, finding the pilgrims in the center, and wiping them out. (First sneak around to the west and then north to find a Sigil of Pain Wardstone in a chest, then continue clockwise to fight the pilgrims near the Sigil of Pain.) Be sure to collect the Horns of the Aurochs before you leave!
 * Talk to Brythe. As it turns out, she didn't expect you to kill everyone, as befitting the Duskspeaker. She will reveal that she was hoping that she could be reconciled with her sister, Ehrys, who was always the surer and smarter of those two. Ydwin will comment on Brythe afterwards, noting that she thinks herself half as clever as she is - and doesn't understand how much cleverer she will have to be.