Summerset Shadows (Quest)

Background
Delvin Mallory tells the Dragonborn of a rival thieves group, the Summerset Shadows. This rival guild needs it to be looked into. In order to obtain this quest, 5 small jobs must be completed in Windhelm for the Thieves Guild.

Walkthrough
Travel to Windhelm and upon arriving, there will be information that there was a brutal murder in Windhelm not long ago. Speak to Torsten Cruel-Sea, who will request the return of the Silver Locket that was taken from his daughter Fjotli's corpse.

Talk to Niranye for more information. With a high enough Speech skill, she can be Persuaded to cooperate, but if this fails, she must be fought and killed. Intimidating her is a more reliable option. Otherwise, the Dragonborn will need "leverage" to get her to talk, which can be found in the form of a note in her house from Linwe.

After getting the location, go to the guild's headquarters in Uttering Hills Cave. The goal is to kill the group's leader Linwe and retrieve Fjotli's Silver Locket. Upon entering the cave tunnels, there will be a fork with left and right paths. Taking the right path will avoid two Summerset Shadows at the end of the tunnel. High-Sneak characters can also sneak past the thieves if taking the left path.

The Locket is found on Linwe's corpse, along with Linwe's Armor Set, a unique set of armor similar in appearance to what some Thieves Guild members wear.

Optional objective
In order to accomplish the extra objective, the Summerset Shadows' banner must be burned. To complete this, simply use a flame spell on the banner (e.g. Flames), the Fire Breath shout or a Torch.

Return to Torsten to finish the quest.

Rewards

 * Enchanted Ring, Circlet or Necklace.
 * Niranye as a fence (if she didn't fight and wasn't killed when talked to)
 * A new merchant just outside of the Ragged Flagon

Trivia

 * The group's name refers to the Summerset Isles, the homeland of the Altmer.

Bugs

 * After accepting the quest, it may not start and won't be present in the quest journal, making the Thieves Guild questline impossible to complete.
 * Normally, Uttering Hills Cave is populated by generic bandits. Once this quest starts, the Summerset Shadows replace these bandits. If the Dragonborn happens to have an outstanding quest to kill the bandits there (a bounty quest from the Jarl, or side quests given by Brunwulf Free-Winter, Annekke Crag-Jumper, and Kjar), it will become impossible to complete once this quest begins, since Linwe will replace the default bandit leader but will not respawn.
 * If this happens, using the console command resurrect on Linwe and then killing him will complete the objective.
 * Torsten Cruel-Sea's map marker can sometimes point somewhere other than where he actually is located.
 * One such location is just to the west of Windhelm, around the base of the mountain, but still "inside" the Windhelm city map cell. If this is the case, enter Windhelm, then use the console command  to float outside of Windhelm's walls and toward the quest marker. Occasionally Torsten will be there inside the mountain right at the marker.
 * Torsten moves around Skyrim at times, and may change locations while the Dragonborn is fast traveling, leading to what appears to be this bug.
 * Sometimes the banner that must be burned will be invisible, but still burnable.
 * Sometimes the optional objective to burn the banner never appears in the journal. If it is burned anyway, Delvin will still mention it.
 * Burning the banner can freeze the game. It will burn normally, but the game freezes when the objective should update. The bug seems consistent for those who encounter it and there are no know solution at this time, save leaving the banner alone. Sometimes, burning the banner and running out of the area immediately, without looking back at it, can avoid this bug.
 * Sometimes Torsten Cruel-Sea will not provide the reward after Fjotli's locket is returned.
 * Sometimes after completing this quest, Niranye never becomes a fence. If the dialog option "How's Business?" is available, select it to make her open her services.
 * If Niranye is dead before the quest is unlocked, the quest becomes unable to complete without her.
 * Fjotli's Silver Locket might not always spawn.
 * Speaking to Delvin after completing the quest will cause him to award 500, even though this does not happen with the other city jobs. He will give 500 every time you leave the Flagon, then return and say you've finished the special Windhelm job.

Sombras de Estivalia Саммерсетские тени (Квест)