Fjola's Wedding Band is a ring and quest item obtained during a miscellaneous quest given by Christer inside Mistwatch. You may find Christer inside a small room hiding. He will task the Dragonborn with finding Fjola inside Mistwatch. Fjola may be found within the topmost tower of Mistwatch. She will be labled with "Bandit Cheif" She then will proceed to ask the Dragonborn why he/she was killing her men. You can then proceed to tell her why you are searching for her.
If the player chooses to get rid of Christer for Fjola, she'll present you with this gift. You also have the option to kill her.