How to Get the 'One with the Shadows' Achievement in The Elder Scrolls V: Skyrim

Are you a member of the Thieves Guild in The Elder Scrolls V: Skyrim? Then this is the achievement guide for you. After you complete the main Thieves Guild quest-line (which is freaking awesome, by the way), you'll be asked to take on special missions. To initiate those, talk to Melvin or Vex in the Thieves Guild headquarters in Rifiten. These small jobs are scattered across the four main cities of Skyrim: Whiterun, Markarth, Solitude, and Windhelm.

Now, you'll need to do four or five missions in each city to receive the special mission for that city. And once you complete all four of the city-specific special missions, you'll be asked to become the guild master. Should you accept (why wouldn't you?), the other main guild members will crown you King of All Thieves. At least, that's what I took it as when they initiated me as guild master.