Ill Met by Moonlight

It is a quest for the Daedric Prince Hircine.

Background
''I've met Sinding, a werewolf who the Daedric Lord Hircine has punished by preventing his transformations. He's given me the ring he stole and asked me to entreat Hircine for forgiveness.''

While in Falkreath, the Dragonborn may hear rumors of the savage murder of a little girl. No one seems quite sure how someone could commit such a horrible crime, but the culprit is currently locked away in the Falkreath jail if the Dragonborn wants to find out.

The Hunt
Sinding (found in Falkreath Jail, under the Barracks) will tell the Dragonborn of a rare animal, the White Stag, that needs to be killed to appease Hircine, the Daedric Prince of the Hunt. Sinding gives the Dragonborn the  Cursed Ring of Hircine, which auto-equips and can't be removed. While worn, it causes the wearer to transform into a werewolf at random, but only if they already have Lycanthropy. Note that transforming will remove all equipped items, including the ring, so transforming once will solve the problem of unpredictable transformations.

After that, Sinding escapes. To remove the cursed ring, the Dragonborn must track down the White Stag and slay it. After doing so, the Stag's spirit appears and approaches the Dragonborn, and Hircine will speak through it. He commands the Dragonborn to go to the place where Sinding has fled, and to kill him to gain the Daedric Lord's favor.

Sinding can be found at Bloated Man's Grotto. After arriving, the Dragonborn will meet some hunters, who are outmatched by the werewolf, Sinding. The Dragonborn can choose to kill Sinding, or to ally with him and kill all the hunters. Note that while in werewolf form, talking with the necessary characters is not possible, so wait for it to wear off.

Reward
The reward received varies depending on the Dragonborn's choices:
 * 1) If Sinding is killed and his skin taken, Hircine appears and rewards the Dragonborn with the Savior's Hide, a leather-based light armor which gives magic and poison resist.
 * 2) If the Dragonborn spares Sinding and kills the hunters, Hircine will appear upon leaving the grotto and commend the Dragonborn for turning the hunt "inside out," giving his blessing and transforming the ring into the Ring of Hircine. This ring gives the Dragonborn unlimited werewolf transformations per day.

It is also possible to obtain both of these rewards using one of a number of similar exploits:
 * Kill all the hunters, speak to Sinding, go outside the grotto and claim the Ring of Hircine, then go back in and kill Sinding to get his skin. The spirit will reappear from Sinding's corpse and offer the Savior's Hide. (Confirmed with latest patch on December 26, 2013 with Dawnguard, Hearthfire, and Dragonborn installed)(Confirmed with latest patch on December 30, 2013 with Dawnguard, Hearthfire, and Dragonborn installed )
 * If the above doesn't work, kill and skin Sinding immediately after killing the hunters and talking to him. As soon as the Hircine spirit appears, back out of the conversation and run out of the grotto where the White Stag spirit will appear and bless the ring to break the curse. Return to the grotto and resume conversation with the Hircine spirit to receive the Savior's Hide. (Confirmed on  as of May 18, 2013)(Confirmed on  as of May 7th, 2013)(Confirmed on  as of May 27th, 2013)
 * A further way that can work to receive both rewards (if the first method results in not being able to skin Sinding upon return and the second method results in a non-speaking Aspect of Hircine in the grotto upon return) is to kill the hunters, kill Sinding near the exit, complete the conversation quickly to claim the Savior's Hide and then sprint to the exit to claim the Ring outside. (Successful when others failed June 10th, with all DLCs and all Unoffical Patches.)
 * Leave the grotto along with Sinding after killing the hunters. When the Stag spirit appears, back out of the conversation and kill Sinding, then skin him and speak with the spirit emerging from his corpse for the Savior's Hide. Speak to the Stag spirit again for the ring.
 * A fourth way to obtain both the ring and the hide, if you originally obtained the ring, is to return to the grotto at any time in the game.  Upon entering the main area you will see Sinding in werewolf form.  Killing this version of Sinding will only result in obtaining ragged trousers.  HOWEVER, if you follow the trail through the grotto, as you did on the original hunt, you will find yourself on a ledge overlooking the main entrance area with a second version of Sinding--one one the ledge with you, and another below.  If you kill the second version of Sinding you receive the option to skin him, causing the aspect of Hircine to appear and convert the skin into the Savior's Hide.  Note: I left the first Sinding alive; I don't know if that matters.  Confirmed on PS3 with all currect updates installed September 15th 2013, having already received the ring about 1/3 of the game earlier.

Conclusion

 * "I met Sinding, a werewolf that the Daedric Lord Hircine had punished by preventing his transformations. I helped kill him as a service to Hircine, and have been rewarded with Savior's Hide."
 * "I met Sinding, a werewolf who the Daedric Lord Hircine had punished by preventing his transformations. I defended him against the hunters that Hircine sent to end his life, and earned his friendship."
 * If Sinding is spared, he may appear in a random encounter later on. He will be in werewolf form and hostile, fighting a hold guard.

Trivia

 * "Ill met by moonlight, proud Titania," is the Fairy King Oberon's first line in A Midsummer Night's Dream, a comedy play written by William Shakespeare.
 * There is also a WW2 book with this name, later made in to a film starring Dirk Bogarde.
 * The White Stag is a reference to King Arthur and the Knights of the Round Table. In the legend, the Stag has a perennial ability to evade capture, and the pursuit of the animal represents mankind's spiritual quest.
 * Both quest rewards count toward the Oblivion Walker achievement. Obtaining both makes the achievement obtainable even if another Daedric quest is failed.
 * If Sinding is killed either before or after helping him kill the hunters, he cannot be resurrected via console after he has been skinned. This is because at that point he has been scripted to die.
 * If the Dragonborn is a vampire during this quest and chooses to kill Sinding for the Savior's Hide, the hunters fighting him may order "Kill the vampire!" even though the Dragonborn is not the target.

Bugs
Зов луны Schicksalstreffen im Mondschein Emboscada nocturna