The Last Pilgrimage

 is a quest in.

Synopsis
Harbinger Brythe is looking for her sister on the Dead Floe, who joined an extremist cult of Rymrgand. She hopes to find and reunite her, before something bad happens.

Walkthrough

 * This is a quest obtained at the Watch, but can only be completed once you reach the eastern cavern of the Rimebound Temple. After fighting your way through a troop of pilgrims, talk to Ehrys in the adjacent construct maintenance area, where she will explain that she came to the Temple to cast off her mortal shell and become a rime construct. Reducing her life to simple instructions carved into her core is, in her mind, the perfect way to worship the Beast: It strips off all pride and falsehood until nothing but the essence remains.
 * You can immediately turn her into a construct, which will result in her becoming a new, mindless construct. You can report to her sister, lying that she died or telling the truth. In the latter case, Brythe will try to find her sister in the temple and be promptly slaughtered by her sibling. To save her, you must convince her to remain at the Watch.
 * Alternatively, you can reunite the sisters. To convince Ehrys, who had a divine revelation atop the iceberg, you need either Religion 8/Mystic background (pointing out that withering and rotting is a better form of worship), Insight 10 (deducing that she simply wants a better body), or a Laborer/Dissident background . Then you need either Religion 15, a Mystic background, or a Monk class (continuing the religious argument) or Diplomacy 14 to persuade her to accept herself. Vatnir can be used to make a case that she can inspire other Harbingers, resulting in an amusing response.
 * If convinced to reunite with her sister, seek her out later at the Watch.