This custom ring was a present for the groom of Castle Delberg. The Princess can find it in the groom's roll bed from the castle kitchens, on the building's ground floor.
Taking the ring will cause an alignment shift of 5 points towards Chaotic.
Spoiler: The inscription on the ring is signed with the letter "F". In the Delberg Castle there is a single character whose name begins with "F", and that is Lady Flora Delberg. The Princess can question Private Perry about this fact. He will confirm the affair and will also provide more details about the failed marriage of Earl Delberg and his wife.