Morrowind:Threads of the Webspinner

Quick Walkthrough
# Talk to Eno Hlaalu at the Hidden Area in the Vivec Arena about the Threads of the Webspinner and the Sanguine items.
# Acquire 26 Sanguine items.
# Return to Eno to complete the quest.

Detailed Walkthrough
thumb|Map showing locations of all 27 items (click to enlarge)
Threads of the Webspinner
Depending on how much exploring of the game you've done, you may have come across a number of Sanguine items that increase various skills when worn. These items are actually part of a collection of 27 created by the Daedra Lord Sanguine for the Morag Tong patron, Mephala. Twenty-six of the items can be found scattered across Vvardenfell - the last, the Amulet of Sanguine Enterprise, is held by the Morag Tong Grandmaster, Eno Hlaalu in Vivec.

The Sanguine Items
Speak with Grandmaster Eno Hlaalu about the items and he will tell you that if you return all of the remaining 26, you will receive an elaborate reward from Mephala. You can return the items to Hlaalu at any time, though you must do so before you become Grandmaster of the Morag Tong and he disappears. Most of the Sanguine items are owned by Dark Brotherhood agents and Mehrunes Dagon worshippers who will generally attack you on sight, meaning you are safe from the law. Unfortunately, Eno will only give you the location of two of the items, so you'll have to find the rest yourself.
 


Non-hostile NPCs
These NPCs are not hostile and have no related quest (see above list for more detail):
Dro'Zaymar, Canal South-Three in the St. Delyn Canton
Gluronk gra-Shula, 2nd floor of Sadrith Mora's Gateway Inn: North Wing
Shotherra, Thongar's Tradehouse in Khuul
Erundil, Indoranyon, on the eastern coast, north of Tel Aruhn

Reward
Once you turn in all 27 Sanguine items to Eno Hlaalu, you are rewarded with Mephala's Skill, a cheap spell that grants Chameleon 50 pts and Fortify Attack 10 pts for 60 seconds for 30 magicka and never fails. This is the only way of acquiring the Fortify Attack effect for creating custom spells.

Notes
The two Sanguine items he asks for directly, Belt of Sanguine Fleetness and Ring of Sanguine Sublime Wisdom, can only be returned once you've been given the special duty for them.
The items are all clothing, and thus unaffected by Disintegrate Armor, so they will always be worn by the character unless they've got something better. Since you can't pickpocket equipped items, killing them is usually the only option. Many are hostile, and some are subjects of other quests, so you can safely kill them anyhow. But a few are peaceful, and some cannot even be taunted into attacking as they will not speak to you. In this case a Frenzy spell may be your best choice to deal with this quest without incurring a large bounty.
Clicking the sanguine enterprise topic may incorrectly report that you've returned all 26 missing threads when you've only returned 25.
You may not notice when the Mephala's Skill has been added. Be sure to check your spell list.
If you complete all the Morag Tong quests and explore the entire island you will most likely have found 22 Sanguine items. The remaining 4 are in the possession of non-hostile NPCs. If you are extremely meticulous about asking people for rumors you will get vague hints for 2 NPCs (Gluronk gra-Shula and Dro'Zaymar). The remaining 2 have no related quests, no rumors and are not hostile. How one is supposed to deduce they have Sanguine items is anyone's guess. Wearing a constant "Detect Enchantment" item and murdering non-hostile NPCs might be the only way to acquire the final two items. One could assume this quest is not designed to be completed in a normal playthrough without resorting to guides.
All of the items you delivered to Eno Hlaalu as part of this quest are stored in his inventory. When you kill him just after finishing this quest, you'll get them back complete for own benefit.
Domba and Gnaw Tooth in Ald Daedroth are severely outmatched by the Witchhunters nearby and will most likely die within seconds of your entry into the Right Wing. If you do not loot their bodies before they despawn, you cannot complete this quest.
For further reading on the Threads of the Webspinner, see the lore article.