Heavy armor not your thing? Prefer stealth to violence? Like to steal shiny things? The Thieves' Guild is the perfect place for you. The guild quests mainly consisting one thing or another from some unsuspecting sucker without getting caught. It also encourages you to rob people on your own and sell your stolen items to special guild vendors.
Tenets
Every guild has tenets that you must follow and the Thieves' Guild is no exception.
Tenet 1: Do not steal from any guild member.
Tenet 2: Do not kill any guild member.
Tenet 3: Do not kill anyone while you're on a guild quest. This is the trickiest one because even if they attack you, you still aren't allowed to kill them. If you do though then you get into the Dark Brotherhood without getting arrested.
Getting Back In
So you broke the rules and now the thieves are mad at you eh? Well as with any good thief money fixes anything so the first time you get kicked out of the guild paying Armand a thousand gold is enough to get back in. It's a bit difficult since you can't turn in stolen loot, but you'll manage.
Joining
The Thieves Guild does not have branches open to the public in the same way as the mages and fighters guilds, so joining is a bit trickier then other guilds.
Method 1: JailBird
To join the Thieves Guild you will first need to accumulate a little jail time. So steal something in the imperial trade district and go to jail when a guard catches you. After your release visit the waterfront district and a female dark elf (Dunmer) should give you a note with where to meet.
Method 2: Ask the Bum
Alternatively you could become good buddies with the beggar in the waterfront district. You'll probably have to bribe him a little. Then ask him about Gray Fox and he'll tell you where the meeting occurs.
The Meeting
For those of you who are too impatient to have to treat this like an actual quest. All you have to do is meet behind one of the houses in the waterfront district at midnight. Just walk around at around 11:30 and talk to the guy with the torch.
List of Fences
Fences are the only people who will buy your ill gotten goods so if you're going to be a thief, team player or not, you'll want to know who and where they are.
Ongar
Ongar will serve any member of the thieves' guild. He sells basic thief stuff (lockpicks, leather armor...) and he'll buy any stolen goods. He usually hangs out in the bar in Bruma.
Dar Jee
Dar Jee will only serve Bandits and above so don't go to him until S'krivva tells you about him. He can be found in Leyawiin.
Luciana Galena
Luciana will only serve Cat Burglars and above so don't go to her until S'krivva tells you about him. She's in Bravil.
Orrin
Orrin will only serve Shadowfeet and above so don't go to him until you start on the Taking Care of Lex quest. He's the Smith at Castle Anvil. Head in and to the right to enter the smithy. He's always there and will buy you're good at any time.
Father Ules
Father Ules will only serve Master Thieves and the Gray Fox so don't go to him until the Gray fox tells you about him. He's in the Imperial City, but he's not very constant, often leaves town, and has been known to glitch and get lost (you can fix that with a fan made patch.)
Thieves' Guild Quests
Most thieves' guild quests are planned heists of specific valuable objects. All quests are assigned by either a Doyen or the guildmaster. A lot of these quests include breaking the law, but if you do it right then you'll get away with it. Also if you are caught in a heist with the item feel free to surrender to the guard they can't take quest items, stolen or not away from you.
Armand Quests
The Thieves' Guild quests are mostly consisting of stealing specific items from targets. Many of them require you to avoid detections or if you do get detected run away. Remember you will be expelled from the guild if you kill someone you're supposed to rob. We're thieves not muggers.
May the best thief win
Upon talking to Armand at midnight he'll say that he's surprised to have 3 recruits at once (there is a Wood Elf and a Argonian are with you as well also trying to join the thieves guild.) He decides to make it a contest and sends all three competitors off to steal Amantius Alectus's diary. He also tells you that you can't kill the other thieves so all you blood thirsty people be warned.
Now you probably have no idea where this guy lives go walk a few feet and you should see the beggar sleeping on a blanket outside. Wake him up and if your buddies with him already (you should be since it's how you join the guild) he'll tell you exactly where your target is and put it on your map.
Method 1
Now you could just try to beat the wood elf there, but there is a much easier way. in the water-front district wait until about 2:00p.m. you should get a message saying she has already found it. Find Methrdhel's house in the waterfront district, break into he house. directly to the left when you open the door is her chest. open it and take the book.
Method 2
For all of you wood elves and people with high speeds it is possible to beat Methrdhel to the book. However, if you want to do this the you need to make sure that you are faster than her. If you can outrun her, then just follow her to the house. Once inside (Save) and look on the first floor for the book.
Method 3
If you are really lazy then just let Methrdhel win, then talk to Armand again and get the other quest
Freelance Work
Now before Armand will give you the second quest you need to sell some ill-gotten goods to a guild member. Now that you're a member of the thieves guild you can sell all that stolen property thus stealling from people actually means something. All quests from here on out will require some kind of money requirement. Example: Before you're assigned the second quest you must have sold 50 gold worth of stolen goods.
Personally I suggest robbing the imperial bookstore. I've yet to do it myself, but while I was in there I couldn't help, but notice so many books worth 10 that weighed next to nothing.
Untaxing the Poor
Well it appears the dastardly Lex has taxed the dead broke people of the waterfront and we can't have that so we'll just have to pull a Robin Hood on him now won't we?
Lex's quarters are in the South Tower (you can get there from the temple district) this mission is a bit odd in that you're going to break into a building where there are always at least 10 guards, but somehow it still works. If you choose to break in during the day then the door is unlocked and no one on the first floor cares about you so proceed to the ladder and go up.
The second and third floors are full of cots that have soldiers sleeping most of the time. If you quickly look around you can find the steps going to the next floor before the guards wake up. The ladder to Lex's room is locked so you'll want to bring some picks on this mission even if you go during the day. Once you're in Lex's room steal anything you want, the tax record and money is in the locked desk (53 gold?!? you might as well beat up a hobo and take his cup of quarters) so now you can leave through the trapdoors leading downward.
Meet Armand's at midnight and give back the tax records, he even says that you can keep the money (the beggar doesn't want his cup of quarters back?) as well as give you another 100 gold.
The Elven Maiden
S'Krivva Quests
After completing the Elven Maiden quest Armand tells you he doesn't have any more work for you and suggest you steal 100 gold worth of goods and go see S'krivva, the other Doyen. S'krivva is usually in her home (in Bravil) reading and lucky for us it's right next to the fast travel point.
Ahdarji's Heirloom
Misdirection
Lost Histories
Taking Care of Lex
Gray Fox Quests
Wow the big man himself is giving us quests now. He's not quite as cool in person as when he was a mysterious symbol. Anyways with each quest he hints at a master plan, a final heist that needs a lot of magical items what could he be up to? Now that you're talking to the boss himself he'll let you ignore one of the tenets, namely killing someone while on the job. The quests from here on out can rarely be pulled off without any fighting and they're also longer dungeon crawls. There are some vampires so take a cure disease potion before bed.
Turning a Blind Eye
Arrow of Extrication
Boots of Springheel Jak
The Ultimate Heist
Aftermath
So now you're the Gray Fox master of thieves' what do ya do now? Well you could just keep on stealing. All guild requirements are now gone, but you can continue adding to your guild tab by selling to your fences.
Guild Headquarters
During the finale of the Ultimate Heist the Gray Fox gave you the guildmaster's key. Head back to where you first met Armand Christophe all those levels ago and unlock the door. Inside you'll find almost all the Imperial City thieves' hanging out and chatting. There are a could of bed mats if you need some rest and a small room with lockpicks on the table.
Head upstairs and you'll find yourself in a fairly nice house. It's got plenty of books and tableware if you want some and a door to the street that doesn't open. Head upstairs again and you'll meet Armand standing outside the door to your room almost 24/7 (this is ideal for paying off bounties you may have racket up in the Imperial City. Head into your room and see a nice bedroom only for you with a comfy bed and some nice items around the room. There's even a wanted posted of the Gray Fox for you to laugh at.
One of the most useful things about the guild headquarters is that only thieves' may enter. No matter how many guards are chasing you when you enter that door you're safe and you can head upstairs and pay off your bounty to Armand.
Being the Gray Fox
Now that you've got the Mask of the Gray Fox you can become him at will. It's a sweet mask that is ideal for thieves. It has detect life (120 feet!) so you always know where the guards are, Feather 200 so you can carry tons more loot, and stealth +25 to make sure you don't get caught. Overall it's the ultimate headgear for a thief.
It naturally comes at a cost though. When donning the mask you become the Gray Fox and thus you're guilty of all his crimes. Guards will swarm to you if you enter a town with it on and give you no choice but to resist arrest. Of course this can be easily avoided, simply take of the mask before they get to you or if you can't get it off that fast simply take it off and yield to the guard. It's endlessly entertaining watching guards rush towards you with the mask on then greet you pleasantly when you take it off.