Upon speaking to Mathies, he explains that Sinding killed his daughter while in werewolf form. Sinding was in Falkreath because he was looking for a giant beast roaming the wilds around the village. If he killed this beast, the Daedric Lord Hircine would lift his curse.
During the quest, the Dragonborn receives the Ring of Hircine from Sinding, which causes the wearer to sporadically transform into a werewolf. When walking away from his cell, a glance backwards will show a werewolf ripping off the bars from the roof, and guards will ask the Dragonborn about him escaping upon leaving the barracks. Killing the transformed Sinding and taking his skin is necessary to obtain the Savior's Hide from Hircine and to remove the Ring of Hircine. Alternatively, Sinding can be spared and the hunters killed, which removes the curse from the Ring of Hircine and allows lycanthropes to use it to transform as many times as desired.
If spared, it seems Sinding is ultimately unable to control his beast blood. If the option to spare Sinding is taken, even if the Dragonborn turned around and killed him as well to complete the quest both ways, he can appear later in a random encounter as a hostile werewolf fighting a guard from the local hold. He can also be encountered in werewolf form, but friendly, in Bloated Man's Grotto.
- If the Dragonborn killed Sinding, a dead werewolf, presumably Sinding, may spawn in the Falkreath Jail at the bottom of the pool.
- If left to live, he may be encountered every month at least once at cleared bandit camps feeding on corpses (it may be possible to find him fighting some bandits in the fort in the overworld, but the forts inside have to be cleared), or at Helgen fighting bandits.
- Falkreath guards will occasionally mention how they know the Dragonborn had something to do with Sinding's escape.
- Sinding's beast form is significantly larger than the player's.
This section contains bugs related to Sinding. Before adding a bug to this list, consider the following:
- He may sometimes be found back in the Falkreath Jail, in werewolf form, after having been spared. Talking to him at this point may cause him to follow the Dragonborn out of jail.
- After the quest, Sinding has a tendency to show up again later:
- Sometimes Sinding follows the Dragonborn out of Bloated Man's Grotto after killing the Hunters during the quest "Ill Met By Moonlight," even after Hircine has given the Ring of Hircine. He will then proceed to roam Skyrim, appearing in various places.
- Sinding will sometimes stay in Bloated Man's Grotto whether killed or not, in the very back of the grotto. When spoken to, he will only reply with "Never thought I'd see you again." or "Until next time."
- Using Healing Hands or Courage on Sinding will cause him to attack the Dragonborn.
- During the quest "Ill Met by Moonlight" if the Dragonborn spares Sinding and talks to him before the quest is finished he will make quiet beeping sounds
- Upon completion of "Ill Met by Moonlight," Sinding, if spared, will not leave the position where he last stood. A second Sinding will spawn inside at the entrance to the Grotto and can be found along with the "original."
- Note: The original copy cannot be killed nor "disabled."
- Upon interacting with Sinding, instead of making any comments or werewolf growls, there is a strange static noise that is heard instead.
- There's a chance after the quest when you go back to falkreath jail with a respawned sinding's and if doing a glitch that will get him out again might not replace the first sinding's in Bloated man's Grotto making it that there is now two sinding's