You'll be rewarded with the trophy once you complete all the storyline relative quests of the Thieves Guild.
Loud and Clear*** Spoiler - click to reveal ***Brynjolf will send you to Goldenglow Estate on a scare and loot mission. There are many optional objectives to be done and each of them makes the mission easier so I suggest to go for them all. First talk to Vex and you will learn about the sewer entrance, which proves very useful to avoid direct confrontation henceforth. You should first head to the beehives to burn three down (with a torch or a flame spell), not a single one more or Brynjolf will cut down your reward. Then proceed into the house. You can try to infiltrate the premises and work on your stealth or rush in, as you see fit. Aringoth will be waiting for you on the second floor. There you can pickpocket the safe key from him, or persuade/intimidate him to give it to you. You may even murder him and loot his warm body if you want. Collect the safe content and return to the Ragged Flagon
Dampened Spirits*** Spoiler - click to reveal ***You wil first have to talk to Maven Black-Briar, who will be at he Bee and Barb, the Meadery or on the throne if the outcome of he civil war made her jarl. She will ask you take part of an elaborate scheme to shut down a competitor. Head to the Bannered Mare in Whiterun and meet Mallus Maccius. Then, go to Sabjorn at the brewery and propose him to perform a pest control. Clear out the skeevers and spiders (also an ostracized mage...) and gain access to the vats so you can poison them. Now witness the tasting ceremony and reap the fruit of your efforts.
Scoundrel's Folly*** Spoiler - click to reveal ***Mercer Frey has a notch that you can learn more about who has been plotting against the guild in Solitude. You will find Gulum-Ei at the Winking Skeever. He will play stupid about the questions you have for him, so persuade or bribe him to get what you want. You might have to do a little fetch job for him. Anyway you will have to follow him into the East Empire Company Warehouse and Brinewater Grotto. Having a high sneak level really helps here, otherwise it is a good opportunity to raise it. When confronted in the end, Gulum-Ei with reveal that Karliah has been behind all this. If you let Gulum-Ei live, he'll become a fence and you'll get the reward from Mercer Frey.
Speaking with Silence*** Spoiler - click to reveal ***So you head toward Snow Veil Sanctum with Mercer Frey to unmask Karliah. Crawl through the dungeon filled with Draugr and tripwire traps. You will find a Word Wall (Disarm) on your way. After you get through the Dragon Claw locked door, the cutscene will start, Mercer's true purpose will be revealed and you will have to carry on with Karliah.
Hard Answers*** Spoiler - click to reveal ***Begin by talking to Enthir in Winterhold, at the Frozen Hearth or the College. You will then have to find Calcemo at the Understone Keep in Markarth. He will agree to open the Museum for you only if you completed a quest in his favor before. Otherwise you have to persuade.bribe/intimidate or pickpocket the key out of him. Then go through the Museum that is much like a dungeon, until you reach Calcelmo's Tower. At the end of the study you will find the stone with the inscriptions. Grab some roll of paper and charcoal from the adjacent office to make a copy of the stone. Get out, avoiding the guards that are looking for you, and return to the Frozen Hearth cellar.
The Pursuit*** Spoiler - click to reveal ***Return to the Ragged Flagon and expose Mercer Frey. You now have to locate the traitor, so go for evidence in Riftweald Manor. If you want to deal with Vald peacefuly you can first go to Maven Black-Briar to erase his debt. Else, use your conventional methods to get past him and get hold of the key. Gain access into the manor, deal with he guards as usual and find the suspicious cabinet on the first floor. Examine it and push its back to reveal a set of stairs leading to tunnels. Explore them fully, retrieve the plans and bring them back to Brynjolf.
Trinity Restored*** Spoiler - click to reveal ***This quest is basically about talking to Karliah, follow her, apply her instructions, talk to her some more, etc... The only noteworthy fact is that you'll become a Nightingale by the end of the quest.[/spoiler
Blindsighted
*** Spoiler - click to reveal ***The Nightingale team is on its way to Irkngthand, the Dwemer ruins where the Eyes of Falmer lie. Get past the usual load of bandits, Dwemer automatons, creatures and traps the dungeon offers until you reach the statue with the Eyes and Mercer Frey. When you reach him, Mercer will incapacitate your team and cast an invisibility spell. Use a Detect Life spell or the Aura Whisper shout to easily spot him. Give him what he deserves and reap the amazing rewards. The cave will then start to be filled with water. Wait until the level rises and a piece of the ceiling falls off, allowing to escape upward. Once out of the heat you are done, or not.
Darkness Returns
Once you get tired of picking locks without any chance of failure, head to Twilight Sepulcher and take the Pilgrim's path. You will first have to confront some Nightingale ghosts, but that shouldn't hold you back very long. The second trial will force you to remain literally in the shadows, as the lighted areas will drain your health away. You will eventually come to a statue of Nocturnal, which you will have to shroud in darkness (you know, take out the lights) to keep onward. You will finally have to get passed some traps and fight some sentinels. When you can at last enter the inner sanctum, the ground will tumble down below you and trap you in a pit. The Skeleton Key should react after a while and you will be able to finish your duty. Upon encounter, Noctural will make you one of her agents, allowing you to choose one of the three powers proposed. You can always come back later and switch if you change your mind about what power is useful to you. Anyway, you have ended this quest by talking to Karliah.