You'll find Aengoth the Jeweler, the local guild head and Thieves Guild quest-giver in "The Rat in the Pot". He's the bearded Bosmer. All of his quests are of the "fetch" variety, but you'll need either exceptional Sneak or some magical backup, or both.
The Mages Guild is going to be unguarded for a while. Why don't you step over there and steal Anareren's Devil Tanto. Take whatever else you'd like while you're at it.
Two problems. First, the Tanto isn't there until he gives you the quest, so no pre-emptive theft. Second "unguarded" is a bit misleading. Everyone who is normally there is gone. Manis Virmaulese is keeping an eye on things in the interim. He's going to be in the entry room and I have *never* been able to get into that building without him detecting me. That's including being stealthed before entering with my Sneak skill boosted to almost 200 points. So I think that initial detection is scripted somehow, even though I don't see a script attached to him for it.
However, if I can get any strength "Chameleon" going once I'm out of his immediate sight, he doesn't detect me again, even after the effect wears off. It just seems to be the when I first enter the building, no matter how I do it.
The Devil Tanto is in a locked chest on a shelf behind the Alchemst's station. Directly across the room is a copy of the Restoration skillbook "Withershins" on a shelft behind the altar. You might want to snag it now because you'll need it for a later quest.
About the only thing you get for this is the goodwill of Aengoth and the Thieves Guild, but you can always sell anthing that you lifted in the process.
A client wants a Redoran Master Helm. Most of the Redoran Councilors have one, but Aengoth knows for sure that there is one in Miner Arobar's room at Arobar Manor. He's right. It's on top of the closet right behind Arobar.
Snag it. But before you leave, go into the room across the hall and take "Boethiah's Pillow Book" from Gandosa Arobar's chest (three chests are behind the screen in front of you - it's the one on the right as the door is behind you). You'll need it for the next quest.
Bring the helm to Aengoth for some goodwill and some gold (about 1000).
A client wants some dirt on Arobar and rumor has it that there is a copy of "Boethiah's Pillow Book" in Gandosa Arobar's bedroom (there is, unless you lifted it during the previous quest). The book has been banned by the Temple, so it should make for sufficient dirt.
There is nothing in the book except a comment that "No words can describe what you see. Or what you think you see", and Aengoth's even more cryptic comment, "Interesting books these Dunmer have." Considering Morrowind's inexplicable fascination with pillows in general, I suspect that it probably describes Boethiah's pillow rather than the more tawdry things that are probably running through your head at the moment. But it's your imagination, so you might as well go for the really satisfying stuff.
Anyway, if you lifted it during the previous quest, Aengoth will simply ask you if it was from Arobar Manor. If you tell him that it is, then he'll pay you for the quest. If you say that you got it somewhere else, he won't.
Your reward is an "Amulet of Far Silence" and a "Chameleon Ring" and the usual warm fuzzies from Aengoth and the Thieves Guild.
A client wants a copy of "Withershins" (a Restoration skillbook). There is one in the possession of Miles Gloriosus at the Andus Tradehouse in Maar Gan (the next stop up the line by Silt Strider from Ald'ruhn), but any copy will do.
In addition to Gloriosus' copy, there is a copy in the Ald'ruhn Guild of Mages (on a shelf behind the altar in the main room), in the Alas Ancestral Tomb, and at Laalam Madalas' house in Sadrith Mora. Copies also turn up as random loot from time to time.
If you snagged the copy from the Mages Guild as I suggested, then it's just a matter of turning it in and collecting your reward (warm fuzzies and 1000 gold). If you didn't, then go grab one and turn it in for your reward.
Just like the other Guildhalls, Ald'ruhn's Thieves Guild is worried about defending itself. Aengoth wants some Centurion Spiders, but needs four sets of scrap metal. Any Scrap Metal will do and you can find it most commonly in Dwarven Ruins, either as ingredients in barrels or as loot drop from the Spiders, Spheres and Centurions roaming around. Some alchemists also carry it in stock and it just so happens that Cienne Sintiene is one of those. Her shop is in the Manor district - the big crabshell in the center of town.
Turn the four portions in to Aengoth for your reward.
Everyone's got it in for the people in Llethi Manor. Helende had you steal a cookbook from them and Aengoth wants you to steal "Darts of Judgment". He says they're arrows, but they're Daedric Darts.
Head on over to Llethi Manor, go down the stairs and turn left to the Guard's Quarters and you'll find them laying on the last bed on the left. The only problem is the three guards who wander the area.
Unlike Helende's measly 250 gold for an enchanted Ebony Staff, Aengoth will pay you the full base price of 500 gold for each one you can retrieve. You'll also get warm fuzzies, but it's 2 points for one dart, 3 points for two, 4 points for three and 5 points for all four. He'll also clear any bounties you might have picked up in the process.
This is Aengoth's last quest.