The Thieve's Guild is a joinable faction in Skyrim. It comes very handy if you are a stealth player, a high sneaking skill is usefull.

Joining has the following Benefits:

• Good Armor sets
• Access to Chillrend, a very powerfull sword
• Fences
• Tonilia, a fence selling Daedric weaponry
• Chests to train Lockpicking.
• Unlimited thievery radiant quests which reward gold
• Master-level training in Lockpicking, Archery, Pickpocket and Sneak
• Guards can be bribed
• The Skeleton Key, an unbreakable lockpick (temporary)
• The Disarm shout

The primary questline consists twelve quests, most of which are blackmailing and courier missions.