Sigilstone of Tribute

Source
This item is a potential reward from the following Class Hall missions:


 * Bring Them Down!
 * Grappling With the Situation
 * Thunder on the Tundra
 * From Helheim
 * Mead Indeed
 * Advanced Taxidermy
 * Stormy Skies

It can also be found inside Curious Wyrmtongue Cache.