Blindsighted Blindsighted is a quest available in . It is the penultimate quest given during the Thieves Guild questline . It is also the quest during which the Skeleton Key is received . Walkthrough . Travel to Irkngthand . Upon arriving at Irkngthand , be wary of the bandits who have set up camp here . It will be necessary to fight a way up to the top to gain entry to Irkngthand . " Note : If this quest has not been started , full entry to this dungeon cannot be attained . ( Dungeon Lock Outs ) Also , any follower with the Dragonborn cannot enter the ruins whilst this quest is active ; they will be waiting for the Dragonborn in Bronze Water Cave . " Speak to Karliah . Once inside , go across the hall and grab the loot in the chest by the fire and bodies . On both sides of the fire are two dwemer chests , one with an adept lock and the other a master lock . Continue on up the stairs . Make a right , then move forward , down the hallway . Go past the water and through the gates into the next hall . To the right at the end of the ledge is an unlocked chest , and another one can be located down near the patrolling sphere . There is also Dwarven Sphere patrolling at the bottom of the stairs . If detected , more of them will come out the holes in the walls , so dispatch them as quietly as possible . ( One way is to use a sneaking bow attack and kill them one by one . ) It is also possible to sneak past the spheres without being noticed . Go to the left of the gate and jump over the fence , then go into stealth and sneak past the one sphere that deployed . In the next room , rotating flame towers will activate . Move around these without making too much noise . The towers are slow enough to sneak through them if timed well . At the final flame tower , go around it to the left and then open the gate to the right of it . Move up the stairs until the master locked gate is reached . In front of the Dragonborn , there will be a ramp with a Dwarven Spider on top . Kill it and hop over the rubble pile to find a hidden chest . Opposite of the master locked gate is a lever . Pull it , and it will open a new area where Karliah and Brynjolf are waiting . Speak to Karliah , and she will explain about the traps that Mercer may have left . Locate Mercer Frey . There will be a trap trigger on the bottom left of the doors in front . Disarm the trap , or open the doors and avoid the flying mace ball trap . On the small table is a bottle of Black - Briar Reserve ( presumably a calling card from Mercer Frey ) , and three lockpicks . Turn left and head down the stairs ; there will also be an expert locked gate full of loot to the left . Karliah will spot Mercer and a short scene will take place . Afterward , follow the path around and open the door , then down until the next hall is reached . Upon entering the next hall , turn right and collect the Falmer chest on the right side next to the Falmer hut , then turn around and head over a small mound to find the lever for the gate below . There is a second lever on the right side , across the large set of facing stairs that must be activated quickly after the first , or it will reset and the door will not open . Once the door is open , travel down the stairs , watching for the spinning blades in the ground , and go through the door . Move through the large area , killing the small groups of enemies . Once at the other end , a collapsed tower can be seen , and it is necessary to go up the spiral ramp and through the door at the top . Before leaving the room , make sure to stop and collect the loot that is in the Falmer chest , which is located next to a Falmer tent to the left on the way to the ramp out . Go down the stairs , carefully avoiding the bear traps . Grab the Detect Life scrolls ; there is one around the table on the floor and two in the room to the right . In the room with the two Detect Life scrolls , there will be writing on the walls from Mercer Frey that says , " " One Step Ahead - Mercer . " " The writing , however , is backwards . Travel through the other gate ( be cautious for more bear traps ) , then through the door at the end of the corridor , which leads to a large hall . Brynjolf will explain that the options are to either sneak around or take on the Dwarven Centurion . Which Centurion the Dragonborn will face is decided by Character Level : 10 – 15 will face a regular Centurion , levels 20 – 30 will most likely be a Centurion Guardian , and levels 45 + will face a Centurion Master . Because there are a lot of Falmer in this room , it is possible to jump off of the small bridge to the right . On the left , there will be a button that activates the Centurion . Activate it , and the Falmer will become hostile and weaken or kill the Centurion with no intervention from the Dragonborn . Regardless of the choice , continue to the cage , and then go up the stairs . There should be a path that leads up and around to the next destination . Be cautions of more Falmer traps . Past the bear traps , there should be some Frostbite Spiders and Falmer across the hall . Once they have been dispatched , collect the loot in the chest next to the Falmer tent at the bottom of the stairs and go through the door leading to the Irkngthand Slave Pens . Go down the stairs and quickly kill the Dwarven Spider , then head left and continue down the stairs . Activate the lever and a spinning blade will take out the two Falmer down below ; remember to turn it off before continuing . Run down the hall , but be careful of the three flame pressure plates near the corner . Once in the next hall , Karliah will say that there are a lot of Falmer in the next room , and will give the option to either sneak or take them on . If it seems easier to sneak past , simply go to the far right - hand side wall and follow it all the way around , into the pen with a small cave at the rear . There is a chest next to the first fire pit in a Falmer tent , and another one in a tent directly across from the first . After the cave , the party will be in a larger cave , with two leveled Falmer in front . Continue down the ramp , and there will be several Chaurus , along with another Falmer . If the Sneak skill is high enough , it is possible to bypass the Chaurus and Falmer by sneaking along the golden pipes above their heads . Continue through the rear of the cave onto a downward hill , making sure to kill the Falmer before dropping down . Head through the gate , then down into Irkngthand Sanctuary . " Note : there are a number of quest - breaking glitches in the next stage , so be sure to create a save before entering the door . " Slaying Mercer Frey . Mercer will be removing the eyes of the statue as the party enters . He will spot the group , and then make the part of the ledge the Dragonborn is standing on collapse . Before the battle begins , he will converse shortly with the Dragonborn about the Thieves Guild and honor before engaging in combat . Mercer will use a Frenzy - type spell on Brynjolf , making him attack Karliah , so they will not be able to help with the fight , as they will be busy with each other . Mercer uses an invisibility spell , so use the Detect Life scrolls , or , if the scrolls were not taken , the Detect Life spell , the Aura Whisper shout , or , if the Dragonborn is a Werewolf , the Scent of Blood power to reveal him and attack . Mercer likes to hit - and - run ; he will turn invisible , sprint up to one of two high points in the room ; by the statue ' s head , or a high spot on the other side of the cavern , behind a pillar . After hiding for a couple seconds , he will spring towards the Dragonborn and inflict one or two power attacks before turning invisible again and retreating . Note that Mercer carries lots of healing , stamina and magicka potions , which he will most likely use during the fight . If in Werewolf form , moving forward while doing a power attack will knock him off of his feet , leaving him defenseless . For a mage , conjuring an Atronach will help , especially a Storm Atronach to drain his magicka , as an Atronach can still " see " him when he is invisible . If the Dragonborn is an archer , the Archery perk , Power Shot , can knock him off balance , preventing him from approaching the Dragonborn as easily . Another way to defeat Mercer is using Windshear , found during the Dark Brotherhood quest , " Hail Sithis ! . " When Mercer casts Invisibility , he will still be under Windshear ' s permanent stagger , and will not move away . After a few strikes , a blood covered silhouette will appear at his location . Once Mercer is dead , loot both the Skeleton Key and Eyes of the Falmer from his body . Escape from Irkngthand . Brynjolf and Karliah will jump down and the chamber will start filling up with water . Once the water is high enough , a rock above the statue ' s head will fall off and open up an area above it . Head into the area , which will lead to an entrance to Bronze Water Cave . Speak to Karliah . Upon speaking to Karliah , she will explain that returning the key will not be easy . The inner sanctum has been locked due to the fact that the Nightingales failed to protect the key in the first place , and the only way through is via the Pilgrim ' s Path . Brynjolf will head back to the guild while Karliah is too afraid to face Nocturnal after her failure , so the Dragonborn must do this alone . After telling the Dragonborn to return the Skeleton Key , she will hand over the Nightingale Bow . Karliah will tell the Dragonborn about the various ' Agent ' aspects that can be assumed at the end of the quest .