Any thieving act such as opening a Thieves Trove or looting a Treasure Chest will open the Thieves Guild skill lines to you in ESO (Elder Scrolls Online). Looting a Treasure Chest will specifically open up the Legerdemain skill line which can be seen as a part of the Thieves guild and stealing from a Thieves Trove will specifically open up the actual Thieves Guild skill line.
You can only acquire the Thieves Guild skill line though if you either own the Thieves Guild DLC or if you have ESO Plus. That's also the only way you can pick up the Main Story Quest of the Thieves Guild and this guide will help you to show how you do this.
In order to start with the Thieves Guild though and effectively leveling your skill line, you will have to play through the Thieves Guild and fulfill dailies.
For this you can open your Collections tab and go to the Zone DLC section. There you will find the Thieves Guild option. If you accept the quest it will ask you to find someone named Quen in any Outlaws Refuge.
Outlaw Refugees have this special sign and you can basically find them in any city.
As soon as you enter the Outlaws Refuge, you should be able to spot Quen pretty easily. She will have the Story Quest marker above her head.
She will ask you to come on a journey with her and to bring some lockpicks. Since they sell them in the Outlaws Refuge, this shouldn’t be any problem if you don’t own them already.
You are then asked to meet her at the docks, from which you will start the quest and somewhat of a tutorial. You will have to sneak and best is also if you already have the Blade of Woe so that you have a much easier time. Visit this tutorial on How to join the Dark Brotherhood to find out how to get the Blade of Woe.
Once you are done with this intro, you will be brought to Abah’s Landing in Hew’s Bane. There you will have to talk to the Thieves Den Guildmaster.
As soon as you have spoken to her you will officially be a part of the Thieves Guild!
We hope you enjoyed the How to join the Thieves Guild guide for ESO (Elder Scrolls Online)!